LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


HAND-BOOK 


TOR 


HEATING  AND  VENTILATING 
ENGINEERS 


BY 


s  D.  HOPPAXAN.  n.  E. 

Professor  of  Engineering  Design 
Purdue  University 


ASSISTED  BY 


BENcJA/niN  P.  RABER,  B.S..  A\.E, 

Instructor  In  Engineering  Design 
Purdue  University 


LAPAYETTE,  INDIANA 


^ 


,vr> 

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COPYRIGHT  1910 

BY 
JAMES  D.  HOFFMAN 


dr\Sr  ^ 

/^   •          Of    THE  1 

I  UNIVERSITY  J 
Vfi 


PREFACE 

In  the  development  of  Heating  and  Ventilating  work,  it  is 
highly  desirable  that  those  engaged  in  the  design  and  the 
installation  of  the  apparatus  be  provided  with  a  hand-book 
convenient  for  pocket  use.  Such  a  treatise  should  cover  the 
entire  field  of  heating  and  ventilation  in  a  simplified  form 
and  should  contain  such  tables  as  are  commonly  used  in  every 
day  practice.  This  book  aims  to  fulfill  such  a  need  and  is 
Intended  to  supplement  other  more  specialized  works. 

These  contents  have  been  compiled,  in  most  part,  from 
lectures  given  to  the  Senior  Mechanical  Engineering  class  at 
Purdue  University  during  the  past  eight  years.  Most  of  this 
material  was  issued  in  pamphlet  form  and  used  as  a  text 
during  the  year  1909-10,  with  very  satisfactory  results.  It 
was  thus  possible  to  criticise  and  remove  errors  that  would 
otherwise  have  appeared  in  the  finished  book.  Because  of 
the  scope  of  the  work,  its  various  phases  could  not  be  dis- 
cussed exhaustively,  but  it  is  believed  that  all  the  fundamen- 
tal principles. are  stated  and  applied  in  such  a  way  as  to  be 
easily  understood.  It  is  suggestive  rather  than  digestive. 
The  principles  presented  are  the  same  as  those  that  have  been 
stated  many  times  before,  but  the  arrangement  of  the  work, 
the  application  and  the  designs  are  all  original.  Many  for- 
mulas and  rules  are  necessarily  given;  but  it  will  be  seen  that, 
in  most  cases,  they  are  developments  from  a  few  general 
formulas,  all  of  which  can  be  readily  understood  and  remem- 
bered. Practical  points  in  constructive  design  have  also  been 
considered.  However,  since  the  principles  of  heating  and 
ventilation  are  founded  upon  fundamental  thermodynamic 
laws,  it  seems  best  to  accentuate  the  theoretical  side  of  the 
work  in  the  belief  that  if  this  is  well  understood,  practical 
points  of  experience  will  easily  follow.  Chapter  16  gives  a 


10 


suggested  arrangement  for  a  course  of  instruction  that  may 
be  used  in  technical  schools. 

It  is  hoped  that  the  material  here  given  will  be  simple 
enough  for  the  beginner  and,  at  the  same  time,  sufficiently 
complete  and  exact  for  the  engineer  with  years  of  experience. 
If  it  merits  the  approval  of  the  reader,  or  if  any  part  is  de- 
fective or  misleading,  we  trust  that  statements  of  approval 
or  criticism,  as  the  case  may  be,  will  be  freely  contributed. 
The  only  way  to  perfect  such  a  book  is  to  have  the  good 
wishes  and  the  co-operation  of  engineers  in  all  branches  of 
the  work.  These  are  solicited. 

All  the  standard  works  upon  the  subject  have  been  freely 
consulted  and  used.  In  most  cases  where  extracts  are  made, 
acknowledgment  is  given  in  the  text.  In  addition  to  this,  ref- 
erences for  continued  reading  are  quoted  at  the  close  of  each 
important  topic.  Because  of  these  references  throughout 
the  book,  we  do  not  here  repeat  the  names  of  their  authors. 
We  wish,  however,  to  express  our  sincere  appreciation  of 
their  valuable  assitance. 
LaFayette,  Indiana.  J,  D.  H. 

September  1,   1910.  B.  F.  R. 


CONTENTS 


CHAPTER  I.     (Heat) 
Arts.  Pages 

1-     4     Introductory.       Measurement     of    Heat    and 

Temperatures     7-   11 

5  Radiation,  Conduction,   Convection 12-  13 

CHAPTER    II.       (Air) 
6-     9     Composition   of   Air.      Amount   Required   per 

Person     14-  21 

10-   13     Humidity 22-   27 

14-   15     Convection  of  Air.     Measurement  of  Air  Ve- 
locities          28-  31 

16-  20     Air    Used    in    Combustion.      Chimneys 32-  33 

References  on  Ventilation 34 

CHAPTER  III.      (Heat   Losses) 

21-  29     Heat    Losses    from    Buildings 35-   41 

30  Temperatures    to    be   Considered 41 

31  Heat  given  off  from  Lights  and  Persons 43 

References  on  Heat  Losses  from  Buildings..  44 

CHAPTER  IV.      (Furnace  Heating) 

32-   34     Essentials  of  the  B  urnace  System 45-   46 

35-   37     Air    Circulation    in    Furnace    Heating 47-  49 

38-   47     Calculations   in   Furnace   Design 49-  51 

48  Application  to  a  Ten  Room  Residence 55-  59 

CHAPTER    V.      (Furnace    Heating,    Continued) 

49-  51  Selecting,  Locating  and  Setting  the  Furnace.  60-  64 
52-  57  Air  Ducts.  Circulation  of  Air  in  Rooms 64-  69 

58  Fan-Furnace      Heating 70 

59  Suggestions    for    Operating    Furnaces 70-   71 

References   on  Furnace  Heating 72 

CHAPTER  VI.     (Hot  Water  and  Steam  Heating) 
60-   65     Comparison   and   Classification   of   Systems..    73-   78 
66-   67     Vacuum   Systems   for  Steam 79-  81 

CHAPTER  VII.  (Ht.  Water  and  St.  Heating,  Cont'd) 
68-   73     Classification  and  Efficiencies  of  Radiators..    82-   86 
74-   77     Heaters  and  Boilers.     Combination  Systems. 

Fittings     87-   92 

CHAPTER  VIII.  (Ht.  Water  and  St.  Heating,  Cont'd) 

78-  80     Calculation  of  Radiator  Surface 93-   99 

81-  84  Pipe  Sizes.  Grate  Area.  Piping  Connections.  99-102 
85  General  Application  to  Hot  Water  Design.  .103-108 
86-  87  Insulating  Steam  Pipes.  Water  Hammer 109-110 

88  Feeding  Return   Water  to   Boiler 110-114 

89  Suggestions    for    Operating    Boilers 114-115 

References  on  Hot  Water  and  Steam  Heating.  116 

CHAPTER  IX.      (Mechanical   Warm  Air  Heating) 
90-  96     General     Discussion.       Blowers     and     Pans. 

Heating     Surfaces J.17-129 

97-   99     Single  and  Double  Duct  Systems.     Air  Wash- 
ing      '. 129-132 


CHAPTER   X.      (Mech.    Warm   Air   Heating,    Cont'd) 

100-104  Heat  Loss.  Air  Required.  Air  Temper- 
atures   133-135 

105-106     Air   Velocities.      Area    of    Ducts 136-137 

107-112  Heating  Surface  in  Coils.  Arrangement  of 

Coils 137-146 

113-114     Amount  of  Steam  Used  in  the  System 146-147 

CHAPTER  XI.      (Mecii.   Warm  Air  Heating,   Cont'd) 

115-121     Air  Velocity  and  Pressure.     Horse  Power  in 

Moving    Air 148-156 

122-124     Fan  Drives.     Speeds.     Size  of  Engine.    Piping 

Connections      157-162 

126  General   Application  to   Plenum   System 163-167 

References   on  Mechanical  Warm  Air  Heat- 
ing      168 

CHAPTER  XII.      (Mechanical  Vacuum  Heating) 

127-131     General.         Webster,  Van  Auken,  Automatic 

and  Paul   Systems 169-179 

References  on  Mechanical  Vacuum  Heating.  180 

CHAPTER  XIII.     (District  Heating) 

132-136     General.         Conduits.         Expansion      Joints. 

Anchors     181-192 

137-139  Typical  Design.  Heat  in  Exhaust  Steam.  .193-199 
140-143  Hot  Water  Systems.  General  Discussion.  ..  .200-202 
144-146  Pressure  and  Velocity  of  Water  in  Mains. .  .203-207 

147-148     Radiation    Heated    by    Exhaust    Steam 207-208 

149-157     Reheater    Calculations 209-216 

158-161     Circulating  Pumps.     Boiler  Feed  Pumps.  ..  .217-223 
162-166     Radiation  Supplied  by  Boilers  and  Economiz- 
ers       223-227 

167  Total  Capacity  of  Boiler  Plant 227-230 

168-170     Cost    of   Heating   from    Central    Station 230-235 

171  Steam    System.      General    Discussion 236-237 

172-174     Pipe    Sizes.      Dripping   the    Mains 237-239 

175  General  Application  of  Steam  System  to  Dis- 
trict   239-241 

References    on    District    Heating 242 

CHAPTER  XIV.     (Temperature  Control) 

176-179  General.  Johnson,  Powers  and  National  Sys- 
tems   243-252 

CHAPTER   XV.      (Electrical    Heating) 

180-182     Discussion   and   Calculations 253-255 

CHAPTER   XVI.      (Course    of    Instruction) 
183-186     Outlines     for    Five    Designs 256-262 

CHAPTER   XVII.      (Specifications) 
187  Suggestions    on    Planning    Specifications 263-269 


APPENDIX 
Tables    and    Diagrams 271-315 


CHAPTER    I. 

HEAT — ITS  NATURE,  GENERATION,  USE,  MEASUREMENT 
AND  TRANSMISSION. 


1.  Introductory: — In  all  localities  where  the  atmosphere 
drops  in  temperature  much  below  60  degrees  Fahrenheit, 
there  is  created  a  demand  for  the  artificial  heating  of  build- 
ings. As  the  buildings  have  grown  in  size  and  complexity 
of  construction,  so  also  this  demand  has  grown  in  extent 
and  preciseness,  with  the  general  result  that  from  the 
antiquated  open  fire-place  and  iron  stove,  there  has  developed 
a  science  growing  richer  each  day  from  inventive  genius 
and  manufacturing  technique — the  science  of  the  Heating 
and  Ventilating-  of  Buildings.  The  purpose  of  this  hand 
book  shall  be  to  outline,  concisely,  the  fundamental  princi- 
ples and  practical  applications  of  this  science  in  its  various 
branches. 

To  the  heating  engineer  of  today,  it  may  be  that  the 
exact  nature  of  heat  itself  is  perhaps  of  less  moment  than 
its  generation  and  transmission,  but  this  much  should  be 
impressed, — that  heat  is  one  form  of  energy,  that  it  cannot 
be  created  except  by  conversion  from  some  other  form,  and 
that  it  is  infallibly  obedient  to  certain  physical  laws  and 
principles. 

In  generating  heat  today  for  heating  purposes,  the 
almost  universal  method  is  combustion.  The  union  of  such 
substances  as  coal,  wood  or  peat  with  the  oxygen  of  the 
air  is  always  attended  by  a  liberation  of  heat  derived  from 
the  chemical  action  of  the  combination;  and  this  heat  is 
carried  by  some  common  carrier,  such  as  air,  water  or 
steam,  to  the  building  or  room  to  be  heated  where  it  is 
given  off  by  the  natural  cooling  process.  In  some  instances 
this  heat  is  converted  into  electrical  energy,  which  is  car- 
ried by  wire  to  the  place  of  use  and  given  off  by  passing 
through  a  set  of  resistance  coils,  which  convert  it  into  heat; 
but  this  method  is  not  much  favored  because  of  its  inef- 
ficiency and  the  resulting  expense.  This  latter  objection 


8  HEATING  AND  VENTILATION 

would  not  hold  in  the  case  of  water  power  installation,  where 
the  combustion  of  fuel  is  entirely  eliminated. 

2.  3Ieasurement  of  Heat: — In  the  measurement  of  heat, 
the  most  commonly  accepted  unit  in  practical  engineering 
work  is  the  British  thermal  unit,  commonly  abbreviated  B.  t. 
u.,  which  may  be  defined  as  that  amount  of  heat  which  will 
raise  the  temperature  of  one  pound  of  pure  water  one  de- 
gree Fahrenheit,  at  or  near  the  temperature  of  maximum 
density,  39.1°  F.  This  unit,  the  B.  t.  u.,  measures  quantity 
of  heat,  while  the  temperature  measures  the  degree  of  heat. 
In  equal  masses  of  the  same  substance  the  two  are  pro- 
portional. The  Fahrenheit  is  the  more  commonly  used  tem- 
perature scale,  especially  in  steam  engineering.  The 
unit  of  this  scale  is  derived  by  dividing  the  distance  on  the 
thermometer  between  the  freezing  point  and  the  boiling 
point  of  water  into  180  equal  degrees,  the  freezing  point  be- 
ing marked  32°,  and  the  boiling  point  212°.  All  temperatures 
in  this  work  will  be  taken  according  to  the  Fahrenheit  scale, 
and  all  quantities  of  heat  expressed  in  British  thermal  units. 

There  is  a  second  unit  of  quantity  of  heat  considerably 
used,  especially  in  scientific  research,  known  as  the  calorie, 
commonly  abbreviated  cal.,  and  defined  as  that  amount  of 
heat  which  will  raise  one  kilogram  of  pure  water  one  de- 
gree Centigrade,  at  or  near  the  temperature  of  maximum 
density,  4°  C.  This  Centigrade  is  a  second  temperature 
scale,  the  unit  of  which  is  derived  by  dividing  the  distance 
on  the  thermometer  between  the  freezing  point  and  the 
boiling  point  of  water  into  100  equal  degrees,  the  freezing 
point  being  marked  0°,  and  the  boiling  point  100°. 

It  is  often  found  desirable  to  change  the  expression  for 
temperature  or  for  quantity  of  heat  from  one  system  of 
terms  to  that  of  the  other.  For  this  purpose  the  following 
formulas  will  be  found  useful: 

F=%C  +  S2    and     C  =  ( .F-32)  £  (1) 

where  F  =  Fahrenheit  degrees  and  0  =  Centigrade  degrees. 
From  these  equations  it  may  be  seen  that  the  two  scales  co- 
incide at  but  one  point,  — 40  degrees.  For  conversion  of  the 
quantity  units  the  following  may  be  used: 

1  British  thermal  unit  =  0.252  Calorie. 

1  Calorie  =  3.968  British  thermal  units. 


MEASUREMENT  OF  TEMPERATURE 


These  are  for  the  absolute  conversion  of  a  certain  quantity 
of  heat  from  one  system  to  the  other.  If,  however,  the 
effect  of  this  heat  is  considered  upon  a  given  weight  of 
substance  and  the  weight  also  is  expressed  in  the  respec- 
tive systems,  the  following  values  hold: 

1  Calorie  per  kilogram  =  1.8  British  thermal  units  per  pound. 
1  British  thermal  unit  per  pound  =  0.555  Calorie  per  kilo- 
gram. 

For  Conversion  tables  from  kilograms  to  pounds  and  vice 
versa,  see  Suplee's  Mechanical  Engineering  Reference 
Book,  page  72,  or  Kent's  Mechanical  Engineers  Pocket  Book, 
page  22. 

3.     3Ieasurement  of  High  Temperatures: — For  the  meas- 
urement  of   temperatures    up    to    the   boiling   point    of   mer- 


Fix.   1. 


d. 


10  HEATING  AND  VENTILATION 

cury,  or  approximately  600°  P.,  the  mercurial  thermometer 
of  proper  range  may  be  employed.  It  is  more  common, 
however,  to  use  some  form  of  pyrometer  for  temperatures 
above  500°  P.,  as  when  the  temperatures  of  stack  gases  or 
of  fire  box  gases  are  desired.  Pyrometers  are  built  upon 
many  different  principles,  the  graphite  expansion  stem  type, 
shown  in  Fig.  1,  a;  the  thermo-electric  type,  shown  in  Fig. 
1,  b;  or  the  Siemens  water  calorimeter  type,  shown  in  F  ig.  1,  c. 
Various  other  methods  might  be  mentioned,  one  of  the  best 
being  temperature  determination  by  the  Seger  cones,  which, 
due  to  varying  compositions,  melt  at  different  temperatures. 
A  line  of  these  numbered  cones  is  exposed  to  the  sweep 
of  the  gases  to  be  measured,  and  their  temperature  de- 
termined very  closely  by  noting  the  number  of  the  last 
cone  which  melts.  The  cones  are  numbered  from  022  to  39 
and  indicate  temperatures  from  590°  to  1910°  F.,  by  ap- 
proximate increments  of  20°.  Fig.  1,  d,  shows  cones  010,  09, 
08  and  07,  of  which  only  the  last  is  unaffected,  and,  from  the 
table  furnished  with  the  cones,  this  indicates  a  temperature 
of  1000°  F. 

4.  Absolute  Temperature: — In  experiments  that  have 
been  carried  on  with  pure  gases  with  the  use  of  air  ther- 
mometers, it  has  been  found  that  air  expands  approximately 
-j.^  of  its  volume  per  degree  increase  in  temperature  at 
zero  F.  or  _1-  of  its  volume  at  zero  C.  From  the  same 
line  of  reasoning,  by  cooling  the  air  below  zero,  the  reverse 
process  should  be  equally  true,  that  is,  for  each  degree 
Fahrenheit  of  cooling  the  volume  at  zero  would  be  contract- 
ed — i Evidently,  then,  if  a  volume  of  gas  could  be  cooled 

to  —  460°  F.,  it  would  cease  to  exist.  This  theoretical  point 
is  called  the  absolute  zero  of  temperature.  All  gases  change 
to  liquids  or  solids  before  this  point  is  reached,  however,  and 
hence  do  not  obey  the  law  of  contraction  of  gases  at  the  very 
low  temperatures.  The  fact  that  air  at  constant  pressure 
changes  its  volume  almost  exactly  in  proportion  to  the  abso- 
lute temperature,  T,  (460  +  t,  where  t  is  temperature  Fahren- 
heit) gives  a  starting  point  to  be  used  as  a  basis  for  all  air 
volume  temperature  calculations.  For  instance,  if  a  volume 
of  20000  cubic  feet  be  taken  in  at  the  air  intake  of  a  build- 
ing at  0°,  and  heated  to  70°,  its  volume,  by  the  heating,  will 


ABSOLUTE   TEMPERATURE   AND   PRESSURE  11 

become  greater  in  the  same  proportion  that  its  absolute  tem- 

x  530 

p.erature  becomes  greater;  that  is,  =:  ;  x  =  23000 

20000  460 

cubic  feet,  or  an  increase  of  15  per  cent. 

GAGE  AND  ABSOLUTE  PRESSURES. — Two  common  ways  of  ex- 
pressing pressures  are  in  use.  One  is  denoted  by  the  expres- 
sion pressure  by  gage,  and  refers  to  the  total  pressure  in 
a  container  minus  the  pressure  of  one  atmosphere.  Thus 
the  expression  "65  pounds  boiler  pressure,  by  gage"  means 
that  the  boiler  is  carrying  65  pounds  pressure,  per  square- 
inch  of  surface,  above  the  pressure  of  the  atmosphere,  which 
is,  for  approximate  calculations,  taken  at  the  standard  pres- 
sure of  14.696  pounds  per  square  inch.  Hence,  the  boiler 
carries  within  it  a  total  pressure  of  65  pounds  plus  14.696 
pounds  or  79.696  pounds  per  square  inch.  This  total  pres- 
sure is  what  is  known  as  absolute  pressure,  and  when  stated  in 
pounds  per  square  foot  of  area,  is  called  specific  pressure. 
Like  the  volume  of  a  gas,  so  also  the  absolute  pressure 
varies  directly  with  the  absolute  temperature/  other  things 
being  constant.  Hence  the  equation  P  V  —  R  T,  where  P 
is  the  absolute  pressure  in  pounds  per  square  foot,  V  is  the 
volume  of  one  pound  in  cubic  feet,  T  is  the  absolute  tem- 
perature, and  R  is  a  constant  which  for  air  is  53.22.  From 
this  equation,  having  given  any  two  of  the  quantities,  P,  V 
or  T,  the  third  may  be  found.  In  very  accurate  calculations 
where  the  value  14.696  is  not  considered  close  enough,  the 
barometer  may  be  read,  and  its  readings,  in  inches  of  mer- 
cury, multiplied  by  the  constant  .49,  to  obtain  the  pressure 
of  the  atmosphere  in  pounds  per  square  inch. 

MECHANICAL  EQUIVALENT  OP  HEAT. — By  precise  experiment,  it 
has  been  determined  that,  if  the  heat  energy  represented  by 
one  B.  t.  u.  be  changed  into  mechanical  energy  without  loss, 
it  would  accomplish  778  foot  pounds  of  work.  Similarly, 
one  calorie  is  equivalent  to  428  kilogrammeters.  One  horse 
power  of  work  is  equivalent  to  the  expenditure  of  33000 
foot  pounds  of  work  per  minute.  Hence  one  horse  power 
of  work  represents  42.416  B.  t.  u.  per  minute. 

LATENT  HEAT. — Not  all  the  heat  applied  to  a  body  pro- 
duces change  in  temperature.  Under  certain  conditions,  the 
heat  applied  produces  internal  or  molecular  changes,  and  is 
called  latent  heat.  Thus  if  heat  is  applied  to  ice  at  the  freez- 
ing point,  no  rise  of  temperature  is  noted  until  all  the  ice 


12  HEATING  AND  VENTILATION 

is  melted;  and  again,  heat  applied  to  water  at  boiling  point 
does  not  raise  the  temperature,  but  changes  the  water  into 
steam.  The  first  is  called  latent  heat  of  fusion,  and  for 
ice  is  142  B.  t.  u.  per  pound,  while  the  latter  is  called  latent 
heat  of  evaporation,  and  for  water  is  969.7  B.  t.  u.  per  pound. 
SPECIFIC  HEAT. — The  ratio  of  the  quantity  of  heat  required 
to  raise  the  temperature  of  a  substance  one  degree,  to  that 
required  to  raise  the  temperature  of  water  one  degree  from 
the  temperature  of  its  maximum  density,  39.1  degrees,  is 
commonly  called  the  specific  heat  of  the  substance.  Table 
15,  Appendix,  gives  'specific  heats  of  substances. 

5.  Radiation,  Conduction  and  Convection: — The  trans- 
mission of  heat,  next  to  its  generation,  forms  an  item  of  vital 
interest  to  the  heating  engineer,  for  different  forms  of  heat- 
ing installations  are  based  fundamentally  on  the  different 
ways  in  which  heat  is  transmitted.  These  ways  are  usually 
quoted  as  being  three  in  number — radiation,  conduction  and 
convection. 

RADIATION. — This  transmission  of  heat  occurs  as  a  wave 
motion  in  the  ether  of  space,  and  is  the  way  by  which  the 
heat  of  the  sun  reaches  the  earth.  Heat  of  this  form,  usu- 
ally referred  to  as  radiant  heat,  requires  no  matter  for  its 
conveyance,  passes  through  some  materials,  notably  rock- 
salt,  without  change  or  appreciable  loss,  and  travels,  as  does 
light,  at  the  rate  of  186000  miles  per  second. 

CONDUCTION. — The  second  method  of  transmission  is  more 
commonly  evident  to  the  senses.  If  a  rod  of  metal  is  heat- 
ed at  one  end,  it  is  known  that  the  heat  is  transferred,  or 
conducted,  along  the  rod  until  the  other  end  becomes  heated 
also.  Conduction  being,  essentially,  the  way  by  which  solids 
transfer  heat,  is  hence  of  special  significance  in  the  calcu- 
lation of  heat  losses  through  the  walls  of  a  building.  Rel- 
ative conductivity  of  a  substance  may  be  defined  as  the 
quantity  of  heat  which  passes  through  a  unit  thickness  of 
the  substance  in  a  unit  of  time  across  a  unit  of  surface  of 
the  substance,  the  difference  of  temperature  between  the 
two  sides  of  the  substance  being  one  unit  of  the  thermo- 
metric  scale  employed.  Since  the  complexity  of  our  build- 
ing constructions  renders  it  obviously  impossible  to  reduce 
all  losses  to  losses  per  unit  thickness  of  the  structure,  we 
are  not  permitted  to  use  the  term  relative  conductivity  but 
another  term,  i.  e.,  transmission  constant,  or  rate  of  trans- 


HEAT  TRANSMISSION 


13 


mission.  Thus  in  Table  IV,  page  36,  the  rate  of  transmission  K, 
given  for  a  6  inch  studded  frame  wall,  is  .25  B.  t.  u.  per 
square  foot  of  surface  per  degree  difference  of  temperature 
for  one  hour.  It  is  readily  seen  that  this  table  is  the  basis 
for  the  heat  loss  calculations  of  buildings. 

CONVECTION. — Gases  and  liquids  convey  heat 
most  readily  by  this  method,  which  is  funda- 
mental with  hot  air  and  hot  water  heat- 
ing installations.  If  it  is  attempted  to  heat 
a  body  of  water  by  applying  heat  to  its  up- 
per surface,  it  will  be  found  to  warm  up 
I.  ^  with  extreme  slowness.  If,  however,  the 

At    _^r  source  of  heat  be  applied  below  the  body  of 

water  as  in  Fig.  2,  it  will  be  found  to  heat 
rapidly,  the  water  being  distributed  by  cir- 
Fig.  2.  culating  currents  having  more  or  less  force, 
and  following,  in  general,  the  direction  shown 
by  the  arrows.  What  actually  happens  is  this: 
— water  particles  near  the  source  of  heat  be- 
come lighter,  volume  for  volume,  than  the  cold- 
er particles  near  the  top;  then,  because  of  the 
change  in  density,  gravity  causes  an  exchange 
of .  these  particles,  drawing  the  heavier  to  the 
bottom  and  allowing  the  heated  and  lighter 
particles  to  rise  to  the  top,  thus  forming  the 
circulation  currents.  This  process  is  known  as 
convection.  It  will  never  occur  unless  the  med- 
ium expands  considerably  upon  being  heated, 
and  unless  the  force  of  gravity  is  free  to  es- 
tablish circulating  currents.  The  hot  water 
heating  system  may  be  considered  merely  as  a 
body  of  water,  Fig.  3,  furnished  with  proper  pipe 
circuits.  When  heated  at  one  point,  the 
water  rises  by  convection  to  the  radiators,  is 
there  cooled,  hence  becomes  heavier,  and  de- 
scends by  the  return  circuit  to  the  point  of  heat 
application,  thus  completing  the  circuit.  The  warm  air 
furnace  installation  works  similarly,  air,  however,  being 
the  heat-carrying  medium. 


n 


Fig.   3. 


CHAPTER  n. 

AIR    COMPOSITION — VENTILATION,    HUMIDITY. 


6.  Composition  of  Atmospheric  Air: — The  subject  of 
ventilation  as  applied  to  buildings  would  naturally  be  in- 
troduced by  a  brief  consideration  of  the  properties  of  the 
air  supplied.  This  supply  is  a  very  important  factor  as  re- 
gards both  quality  and  quantity.  In  addition  to  its  value 
as  a  heating  medium,  it  determines,  in  a  large  measure,  the 
health  of  the  occupants  of  the  building. 

The  human  body  may  be  considered  as  a  well  equipped, 
although  very  complex,  power  plant.  As  the  carbon,  hydro- 
gen and  oxygen  in  the  fuel  and  air  supply  in  any  mechan- 
ical power  plant  are  consumed  in  the  furnace,  the  resulting 
heat  absorbed  in  the  generating  system  and  finally  turned 
into  work  through  the  attached  mechanisms,  so  the  human 
body  in  a  similar  way,  but  at  a  much  slower  rate,  absorbs 
the  heat  of  combustion  and  turns  it  into  work.  The  prod- 
ucts of  combustion  in  both  cases  are  largely  carbonic  acid 
and  water.  The  chief  requisites  of  the  mechanical  plant 
are  good  fuel,  good  draft  and  good  stoking.  Similarly,  the 
human  body  needs  pure  food,  pure  air  and  healthful  exer- 
cise. Of  the  three,  the  second  is  probably  of  the  greatest 
importance,  since  no  person  can  keep  in  health  with  im- 
pure air,  .even  though  accompanied  with  the  best  of  food 
and  plenty  of  exercise. 

Air,  to  the  average  person,  is  made  up  of  two  elements, 
oxygen  and  nitrogen,  in  the  volume  ratio  of  about  20.9  to 
79.1  and  a  density  ratio  of  about  23.1  to  76.9,  respectively. 
We  find  in  making  a  complete  analysis  of  pure  air,  that  a 
number  of  other  elements  and  compounds  enter  into  it,  mak- 
ing a  mechanical  mixture  which  is  somewhat  complex.  To 
the  heating  and  ventilating  engineer,  however,  two  im- 
portant substances  must  be  added  to  the  two  just  stated, 
and  a  revision  of  the  percentages  will  therefore  be  neces- 
sary. It  may  be  said  that  pure  air,  as  taken  from  the  good 
open  country  and  not  contaminated  with  poisonous  gases 
or  the  dust  and  refuse  from  the  cities,  would  have  about 


COMPOSITION  OP  AIR  15 

the     following     composition.     See     Encyclopedia    Britannica, 
Respiration. 

Oxygen  Symbol    O          Per  cent,  of  volume  20.26 

Nitrogen  "         N  "         "        "  78.00 

Moisture  "         H2O  "          "        "  1.7 

Carbonic   Acid  "         CO2  "          "        "  .04 

These  values  are  fairly  constant,  except  that  of  the  mois- 
ture, which  may  vary  according  to  the  humidity  anywhere 
from  0  +  to  4  per  cent,  of  the  entire  weight  of  the  air.  In 
places  where  the  air  is  not  pure,  the  following  substances 
may  be  found  in  small  quantities:  Carbon  Monoxide  (CO), 
Sulphuretted  hydrogen  (H2S),  Ozone,  Argon,  compounds  of 
Ammonia,  and  compounds  of  Nitric,  Nitrous,  Sulphuric  and 
Sulphurous  acids. 

In  the  process  of  respiration,  the  lungs  and  the  skin 
of  the  average  person  will  change  the  composition  of  the 
air  from  that  given  above  to 

Oxygen                           Per    cent,  of  volume  16 

Nitrogen                                    "  "  "  75 

Moisture  5 

Carbonic  Acid                       "  "  "  4 

Comparing  these  values  with  those  for  pure  air,  it  will 
be  seen  that  the  oxygen  has  been  reduced  about  one-fifth, 
the  nitrogen  has  been  reduced  about  one  twenty-fifth,  the 
vapor  has  increased  three  times  and  the  carbonic  acid  has 
increased  one  hundred  times.  Oxygen  has  been  consumed 
in  its  uniting  with  the  excess  carbon  and  hydrogen  in  the 
system,  and  is  given  off  as  carbonic  acid  and  water  vapor. 
It  may  be  seen  from  these  ratios,  that  the  very  rapid  increase 
in  carbonic  acid  (rejected  bodily  tissue),  would  soon  render 
unfit  for  use  the  air  in  almost  any  building  occupied  by  a 
number  of  people.  To  avoid  this  state  of  affairs,  fresh  air 
should  be  supplied  continuously  and  at  such  points  as  will 
provide  the  most  uniform  circulation. 

7.  Oxygen  and  Nitrogen: — The  oxygen  of  the  air  fills 
about  one-fifth  of  the  volume  in  atmospheric  air  and  is  the 
element  that  makes  combustion  possible.  The  other  four- 
fifths  of  the  space  might  be  said  to  be  filled  with  nitrogen. 
In  a  providential  way,  this  nitrogen  acts  as  a  sort  of  buffer 
in  its  mixture  with  the  oxygen  and  serves  to  control  the 
rapidity  with  which  the  combustion  takes  place.  Nitrogen 
seems  to  have  little  effect  upon  the  respiration,  except  to 
retard  the  chemical  action  between  the  oxygen  and  carbon 


16  HEATING  AND  VENTILATION 

and  the  oxygen  and  hydrogen.  If  one  were  to  attempt 
to  live  in  an  atmosphere  of  pure  oxygen,  the  chemical  action 
in  the  lungs  would  be  so  rapid  that  the  human  body  would 
not  be  able  to  maintain  it. 

8.  Carbonic  Acid: — The  amount  of  carbonic  acid  or 
carbon  dioxide  as  it  is  sometimes  called,  as  found  in  the 
air,  is  used  as  an  index  to  the  purity  of  the  air.  This  is 
not  considered  a  poisonous  gas.  The  real  action  of  the  car- 
bonic acid  when  taken  into  the  system  is  not  well  known. 
It  has  the  effect  of  producing  physical  depression,  and 
where  fpund  in  sufficient  quantity  would  even  cause  death. 
Whatever  its  effect  upon  human  life  may  be,  its  presence  in 
any  room  used  for  habitation  i's  usually  an  indication 
of  the  lack  of  oxygen.  Pure  air  has  four  parts  carbonic 
acid  in  10000  parts  of  air,  and  room  air  should  never  be 
allowed  to  have  more  than  eight  to  ten  parts  in  10000  parts 
of  air.  It  becomes  the  problem  of  the  heating  engineer, 
therefore,  to  provide  air  in  sufficient  quantities,  and  to  enter 
and  withdraw  the  air  from  the  room  in  a  manner  such  as 
will  not  be  uncomfortable  to  the  occupants,  at  the  same 
time  keeping  the  air  fairly  uniform  in  quality,  throughout 
the  room.  Carbonic  acid  in  the  exhaled  breath  is  about 
five  times  heavier  than  air,  and  therefore,  would  have  a 
tendency  to  fall.  It  is  exhaled,  however,  with  excessive 
moisture  and  at  a  temperature  higher  than  that  of  the  room 
air,  both  qualities  giving  it  a  tendency  to  rise.  These  latter 
factors  probably  neutralize  the  excessive  density,  and  as 
long  as  the  air  is  not  absolutely  quiet,  the  result  is  a  fair 
diffusion  throughout  the  room  air.  In  large  audiences  the 
heat  given  off  from  the  occupants  is  sufficient  to  cause  strong 
air  currents  which,  in  rising,  lift  this  impure  air  to  the  upper 
part  of  the  room. 

A  method  of  determining  the  percentage  of  carbon  dioxide  in  the 
air,  based  upon  the  fact  that  barium  carbonate  is  nearly  in- 
soluble in  water,  may  be  performed  as  follows:  Provide 
eleven  bottles  with  rubber  stoppers  having  two  holes  each, 
and  connect  them  continuously  by  glass  and  rubber  tubing, 
so  that  if  suction  be  applied  at  the  first  bottle  of  the  series, 
air  will  be  drawn  in  at  the  last  of  the  series  and  the  same 
air  will  be  passed  through  all.  In  this  way  a  sample  of  the 
air  to  be  tested  may  be  drawn  into  each  bottle.  The  capac- 
ities of  the  bottles  must  be  mad.e  to  be  respectively,  in 
ounces,  23%,  18%,  16%,  14,  9%,  7%,  5%,  4,  3%,  2%  and  2. 


DETERMINING  THE   PURITY   OF  AIR 


17 


This  may  readily  be  done  by  partially  filling  with  parafflne. 
Into  each  bottle  is  then  placed  %  ounce  of  a  50  per  cent,  sat- 
urated solution  of  barium  hydrate,  Ba(OH)2.  More  of  the 
air  to  be  tested  is  drawn  through  the  system  until  assurance 
is  had  that  each  bottle  contains  a  fair  sample.  Each  bottle  is 
then  thoroughly  shaken,  so  that  the  liquid  may  be  brought 
into  good  contact  with  the  air  sample.  If  the  least  turbidity 
or  cloudiness  appears  in  the 

'First  or  largest  bottle  indicates  0.04  per  cent.  CO2 

Second    bottle  indicates  0,06  "         "         " 

Third           "  "  0.07  " 

Fourth        "  "  0.08  " 

Fifth            "  "  0.10  "         "         " 

Sixth            "  "  0.15     

Seventh  "  "  0.20  " 


Eighth 
Ninth 
Tenth 
Eleventh 


0.30 
0.40 
0.60 
0.90 


Care  must  be  taken  to  have  a  fair  sample  of  the  air  in 
each  bottle.  The  glass  tubes  through  the  rubber  stoppers 
should  extend  no  farther  than  the  bottom  of  the  stoppers. 
Fig.  4,  a,  shows  four  of  the  bottles  and  their  connections. 

As  an  example,  suppose  that  the  air  of  a  room  was  tested 
and  that  in  the  first,  second,  third,  fourth,  fifth  and  sixth 
bottles  the  liquid  became  turbid  after  vigorous  shaking. 
Such  room  air  would  have  contained  0.15  per  cent,  of  carbon 
dioxide,  and  would  have  been  considered  quite  unfit  for 
breathing. 


Fig.    4. 


18  HEATING  AND  VENTILATION 

A  second,  less  cumbersome,  and,  more  delicate  method  of  testing 
for  the  percentage  of  carbon  dioxide  will  be  described,  as  it  is 
the  method  commonly  used  and  only  requires  comparatively 
simple  apparatus,  as  shown  in  Fig.  4,  (b).  A  bottle  of 
about  6  ounces  capacity  is  fitted  with  a  rubber  stopper  hav- 
ing two  holes.  Through  one  hole  a  glass  tube  is  brought 
from  the  bottom  of  the  bottle,  and  to  the  outer  end  of  the 
tube  is  connected  a  valved  bulb  similar  to  those  found  on 
atomizers.  Into  the  bottle  are  placed  10  cubic  centimeters 
of  a,  solution  made  by  dissolving  .53  grams  of  anhydrous 
sodium  carbonate,  Na2  CO3,  in  5  liters  of  water,  and  adding 
.01  gram  of  phenolphthalein.  The  water  used  must  have  been 
previously  boiled  for  at  least  one  hour  in  an  open  vessel. 
With  the  apparatus  so  prepared,  squeeze  the  bulb,  thus  forc- 
ing air  from  the  room  through  the  liquid  and  into  the  bot- 
tle. The  open  hole  in  the  rubber  stopper  is  then  closed  with 
the  thumb,  and  the  bottle  shaken  while,  say,  twenty  is 
counted,  then  another  bulb-full  of  air  is  inserted,  and  again 
shaken.  This  process  is  continued  and  the  number  of  bulbs 
of  air  noted  until  the  red  color  of  the  solution,  due  to  the 
phenolphthalein,  disappears.  This  number  of  bulb  fillings  is 
indicative  of  the  purity  of  the  air  according  to  the  table 
below.  After  such  an  apparatus  is  completed,  it  must  be 
calibrated  before  being  used.  This  is  done  by  testing  the 
number  of  bulb  fillings  of  pure  country  air  necessary  to 
clear  the  liquid,  which  will  usually  vary  from  40  to  70.  A 
new  table  for  that  special  apparatus  is  then  obtained  from 
the  one  given  below  by  proportion.  In  the  table  given,  this 
number  of  bulb  fillings,  with  purest  country  air,  is  48.  If, 
with  the  apparatus  made  up,  it  is  found  that,  say,  60  bulb 
fillings  are  required,  then  the  proportionate  table  would  be 
made  by  multiplying  the  number  of  bulb  fillings  given  below 
by  the  ratio  of  60  -r-  48,  or  5  to  4.  It  is  important  that  the 
bulb  be  compressed  the  same  amount  for  each  filling,  and 
that  the  shaking  of  the  bottle  and  contents  be  continued 
the  same  length  of  time  after  each  filling,  to  obtain  uniform 
results. 


DETERMINING  THE  PURITY  OF  AIR  19 

TABLE   I. 

Fillings               Per  Cent  CO2  Fillings           Per  Cent  COa 

48  .030  13  .08 

40  .038  12  .083 

35  .042  11  .087 

30  .048  10  .09 

28  .049  9  .10 

26  .051  8  .115 

24  .054  7  .135 

22  .058  6  .155 

20  .062  5  .18 

19  .064  4  .21 

18  .066  3  .25 

17  .069  2  .30 

16  .071 

15  .074 

14  .077 

The  methods  outlined  for  the  approximate  estimation  of 
CO2  are  satisfactory  for  determining  whether  or  not  ventila- 
ting systems  maintain  a  proper  degree  of  purity  of  air.  If 
exact  percentages  of  CO,  CO2,  O  and  N  are  required,  the  Orsat 
apparatus  must  be  employed,  for  description  of  which  see 
Engineering  Chemistry  by  Stillman,  page  238.  See  also  Car- 
penter, H.  &  V.  B.,  Chap.  II,  and  Hempel's  Gas  Analysis,  tran- 
slated by  Dennis. 

9.  Amount  of  Air  Required  per  Person: — The  need  of  a 
continuous  supply  of  fresh  air  in  our  residence  and  business 
houses  can  scarcely  be  over-estimated.  Health  is  probably 
the  greatest  of  all  blessings  and  pure  air  is  absolutely  es- 
sential to  health.  The  average  adult,  when  engaged  in  or- 
dinary indoor  occupations,  will  exhale  about  twenty  cubic 
inches  of  air  per  respiration.  He  will  also  have  sixteen  to 
twenty  respirations  per  minute,  making  a  total  of  400  cubic 
inches  or,  say,  .25  cubic  foot  of  air  exhaled  per  minute.  If 
as  in  Art.  6,  exhaled  air  contains  4  per  cent.  CO2,  then 
the  average  person  will  exhale  60  x  .25  x  .04  =  .6  cubic  foot 
CO2  per  hour,  (Pettenkofer,  Smith  &  Parker),  which  is  con- 
stantly being  diffused  throughout  the  air  of  the  room,  thus 
rendering  it  unfit  for  use.  If  this  carbonic  acid  gas  could 
be  disassociated  from  the  rest  of  the  air  and  expelled  from 
the  room  without  taking  large  quantities  of  otherwise  pure 
air  with  it,  the  problems  of  the  heating  engineer  would  be 


20  HEATING  AND  VENTILATION 

simplified,  but  this  cannot  be  done.  Because  of  this  rapid 
diffusion,  it  is  necessary  to  flood  the  room  with  fresh 
air  in  order  that  the  purity  may  be  maintained  at  a  safe 
value.  The  ideal  conditions  "would  be  to  have  it  the  same 
as  that  of  the  outside  air,  but  the  mechanical  difficulties 
around  such  a  ventilating1  system  would  be  so  great  as  to 
render  it  prohibitive.  The  standard  of  purity  which  should 
be  aimed  at,  and  one,  as  well,  which  may  be  attained  with  a 
first  class  system,  is,  .06  of  one  per  cent.  CO2,  i.  e.,  six  parts 
of  CO2  in  10000  parts  of  air.  A  system,  however,  which 
maintains  a  standard  of  eight  parts  in  10000  would  be 
considered  fairly  satisfactory.  This  may  be  put  in  a  simple 
form  for  calculation. 

Let  QL  =  cubic  feet  of  atmospheric  air  needed  per  hour 
per  person;  A  =  cubic  feet  of  COa  given  off  per  hour  per 
person;  n  —  the  standard  of  purity  to  be  maintained  (al- 
lowable parts  of  COo  in  10000  parts  of  air);  and  p  =  the 
standard  of  purity  in  atmospheric  air,  say,  4;  then 


If  we  wish  to  maintain  a  purity  in  the  room  of  seven 
parts  CO3  in  10000  parts  of  air,  and  pure  air  contains  four 
parts  in  10000,  we  have  Qi  =  .  6  4-  (.0007  —  .0004)  =  2000 
cubic  feet  of  air  per  hour. 

Another  formula,  quoted  from  Carpenter's  Heating  and 
Ventilating  of  Buildings,  very  similar  to  the  above,  is 


where  a  =  the  purity  of  the  exhaled  breath,  say  400  parts 
in  10000,  n  —  the  purity  to  be  maintained  in  the  room  and 
6  =  the  cubic  feet  of  air  exhaled  per  minute.  Substituting, 
as  above, 

QL  =  (400  X  60  X   .25)  -=-  (7  —  4)  =  2000  cubic  feet. 

Based  upon  .6  cubic  foot  of  COs  exhaled  per  person  per 
hour,  Table  II  gives  the  amount  of  air  needed  to  maintain 
the  various  standards  of  purity. 

It  should  be  understood  that  no  hard  and  fast  rule  can 
be  given  for  the  air  requirement  per  person.  This,  natur- 
ally, would  be  a  different  amount  when  considering  the 
physical  development  for  each  person  in  health;  it  would 
also  be  different  for  the  same  person  according  to  his  occu- 


AIR    REQUIRED    PER    PERSON  21 

pation  at  the  time,  sleep  being  the  least,  waking  rest 
somewhat  greater,  and  physical  exercise  the  greatest;  but 
it  is  decidedly  varying  when  considering  the  state  of  the 
person's  health,  or  the  sanitary  value  of  his  surroundings. 
According  as  the  degree  of  purity  is  demanded,  the  air 
supply  must  be  increased  to  suit  it. 

TABLE    II. 
Cubic  F  eet   of  Air  per  Person   per   Hour. 


n 

A 

Qi 

6 

.6 

3000 

7 

.6 

2000 

8 

.6 

1500 

9 

.6 

1200 

10 

.G 

1000 

Generally,  it  is  understood  that  the  average  adult  sub- 
jected to  average  conditions  will  require  1800  cubic  feet  of  air 
per  hour.  The  amount  of  air  needed  for  ventilation  then  in 
most  cases  can  be  represented  by  the  formula  Q'  =  1800  N, 
wnere  N  =  the  number  of  people  to  be  provided  for. 

The  following  table  quoted  from  Carpenter's  H.  &  V.  B., 
and  from  Morin  in  Encyclopedia  Britannica,  gives  a  fair 
value  for  the  amount  of  air  per  occupant  per  hour,  that 
should  be  supplied  to  rooms  used  for  various  purposes. 

TABLE    III. 


Hospitals,  Ordinary 2000-2400  cu.   ft.  per  hour. 

"  Epidemic    5000  "      "       "          " 

Work     Shops,     Ordinary 2000  "      " 

Unhealthy  trades   ..3500 

Prisons    1700 

Theaters 1400-1700    "      " 

Meeting   halls    1000-2000 

Schools,   per   child 400-   500    "      " 

adult 800-1000    "       " 

Recent    practice    would    tend    to    increase    these    values 
somewhat;   especially  those  relating  to  school   bouse  ventll- 


22  HEATING  AND  VENTILATION 

ation,  where  a  good  estimate  would  be  800  to  1800  respec- 
tively. 

One  ordinary  gas  burner  of  20  candle  power,  using,  say, 
four  cubic  feet  of  gas  per  hour,  will  vitiate  as  much  air 
as  three  or  four  people.  Where  many  lamps  are  used,  this 
fact  should  be  taken  into  account. 

In  summing  up  the  subject  of  ttie  fresh  air  supply,  it  is  well  to  call 
attention  to  the  fact  that  the  ordinary  running  conditions  of 
any  room  cannot  be  absolutely  determined  by  a  single  test  for 
carbon  dioxide.  Trials  should  be  frequently  made  and  rec- 
ords kept.  Upon  one  day  the  conditions  may  be  unusually  fav- 
orable and  would  show  a  small  amount  of  CO2  even  though  a 
very  small  amount  of  fresh  air  be  admitted;  while  on  other 
days,  when  the  conditions  are  not  so  favorable,  a  large 
amount  of  fresh  air  would  have  to  be  supplied  to  maintain 
the  proper  purity  within.  If  the  only  requirement,  therefore, 
governing  the  ventilation  of  buildings  should  be  that  a  satis- 
factory CO2  test  be  passed,  there  would  be  a  large  oppor- 
tunity to  overrate  or  underrate,  as  the  case  may  be,  the  ven- 
tilating system  of  the  building.  The  only  safe  method  in  rating 
ventilating  systems  is  to  require  a  minimum  air  supply  in  addition  to  a 
maximum  permissible  percentage  of  C02, 

10.  Moisture  with  Air: — Moisture  with  the  air  is  a  benefit 
to  both  the  heating  and  ventilating  systems  in  any  room. 
With  moisture  in  the  room,  a  person  may  feel  comfortable 
when  the  temperature  is  several  degrees  lower  than  the 
comfortable  temperature  of  dry  air.  Dry  air  takes  up  the 
moisture  from  the  skin.  The  vaporization  of  this  moisture 
causes  a  loss  of  heat  from  the  body,  and  gives  to  the  per- 
son a  sense  of  cold,  which  is  only  relieved  when  the  tem- 
perature of  the  room  is  increased.  Air  space  that  is  fairly 
saturated  with  moisture  will  not  permit  of  much  evaporation 
from  the  skin,  because  there  is  not  much  demand  for  this 
moisture  with  the  air;  consequently  the  body  retains  that 
heat  and  the  person  has  a  sensation  of  warmth  which  is 
only  relieved  by  lowering  the  temperature  of  the  air  of  the 
room.  On  the  other  hand,  at  low  temperatures  the  mois- 
ture with  air  chills  the  surface  of  the  skin  by  convection, 
a  condition  that  is  not  so  noticeable  when  the  air  is  dry. 
It  follows  from  the  above  statement  that  the  range  of  com- 
fortable temperatures  is  less  for  moist  air  than  for  dry  air. 

Concerning  the  effect  of  moisture  in  its  relation  to  the 
heating  and  ventilating  of  the  room,  we  may  say  that  thor- 


MEASUREMENT  OF  HUMIDITY 


23 


oughly  dry  air  has  not  the  quality  of  intercepting-  radiant 
heat;  moisture,  however,  has  this  quality.  Moist  air  has 
also  somewhat  less  weight  than  dry  air  and  is  more  buoyant. 
Because  of  the  possibility  of  storing  up  the  radiant  heat 
within  the  particles  of  moisture,  and,  because  of  its  con- 
vection qualities,  it  serves  as  a  good  heat  carrier  for  the 
heating  system. 

11.  Humidity  of  the  Airt — The  actual  humidity  is  the 
amount  of  moisture  expressed  in  grains  or  in  pounds  per 
cubic  foot,  mixed  with  the  air  at  any  temperature.  The 
relative  humidity  is  the  ratio  of  the  amount  of  moisture  actu- 
ally with  the  air  divided  by  the  amount  of  moisture  which 
the  same  volume  could  hold  at  the  same  temperature  when 
saturated.  It  is  very  important  that  the  heating  engineer 
be  able  to  add  to  or  to  take  away  from  the  amount  of  the 
moisture  in  the  air  supply  of  any  building.  To  find  the 
amount  of  moisture  that  should  be  added  or  subtracted  in 
any  case,  it  is  first  necessary  to  determine  the  humidity  of 
the  air  current  at  various  points  along  its  course.  This 
may  be  obtained  by  the  aid  of  the  wet  and  dry  bulb  ther- 
mometer or  by  any  one  of  a  number 
of  hygrometers  supplied  by  the 
trade.  The  wet  and  dry  bulb  ther- 
mometer has  a  very  simple  appli- 
cation, and  is  probably  in  most  gen- 
eral use.  The  principle  of  its  ap- 
plication is  as  follows:  having  two 
thermometers,  Fig.  5,  let  one  of 
them  register  the  temperature  of 
the  room  air,  the  other  one  being 
kept  wet  by  a  cloth  which  covers 
the  bulb  and  projects  into  a  vessel 
filled  with  water,  shown  between 
the  two  thermometers.  If  the  air 
Is  saturated  the  two  thermometers 
will  record  the  same  temperature; 
if,  however,  the  air  is  not  saturated 
the  thermometer  readings  will  dif- 
fer an  amount  depending  upon  the 
Fig.  5.  humidity.  It  will  readily  be  seen  that 

the  lowering  of   the   temperature   in 

the  wet  thermometer  is  due  to  the  extraction  of  the  heat 
in  vaporizing  the  moisture  from  the  bulb  to  the  air. 


24  HEATING  AND  VENTILATION 

In  taking  readings,  let  the  mercury  find  a  constant  level 
In  each  thermometer  and  then  note  the  difference  in  temper- 
ature between  the  two.  In  Table  10,  Appendix,  at  this 
difference  and  at  the  room  temperature  read  off  the  relative 
humidity;  then  take  from  Table  9,  Appendix,  the  amount 
of  moisture  with  saturated  air  at  the  temperature  recorded 
by  the  dry  thermometer,  and  multiply  this  by  the  humidity. 
The  result  is  the  amount  of  moisture  with  the  air  per  cubic 
foot  of  volume. 

APPLICATION. — Room  air,  70  degrees;  difference  in  readings, 
6  degrees.  From  Table  10,  the  humidity  is  72  per  cent. 
From  Table  9,  col.  7,  .72  X  .001153  =  .00083  pounds  per 
cubic  foot. 

To  avoid  the  necessity  for  the  use  of  tables,  various  in- 
struments have  been  designed,  which,  graphically,  give  the 
relative  humidity  directly.  Fig.  6,  shows  such  an  instrument, 


Fig. 

commonly  known  as  the  Jiygrodeik.  To  find,  by  it,  the  relative 
humidity  in  the  atmosphere,  swing  the  index  hand  to  the 
left  of  the  chart,  and  adjust  the  sliding  pointer  to  that  de- 
gree of  the  wet  bulb  thermometer  scale  at  which  the  mer- 
cury stands.  Theoi  swing  the  index  hand  to  the  right  until 


MEASUREMENT  OP  HUMIDITY  25 

the  sliding  pointer  intersects  the  curved  line  which  extends 
downward  to  the  left  from  the  degree  of  the  dry  bulb 
thermometer  scale,  indicated  by  the  top  of  the  mercury 
column  in  the  dry  bulb  tube.  At  that  intersection,  the  in- 
dex hand  will  point  to  the  relative  humidity  on  scale  at  bot- 
tom of  chart.  Should  the  temperature  indicated  by  the  wet 
bulb  thermometer  be  60  degrees  and  that  of  the  dry  bulb 
70  degrees,  the  index  hand  will  indicate  humidity  of  55 
per  cent.,  when  the  pointer  rests  on  the  intersecting  line 
of  60  degrees  and  70  degrees. 

For  accurate  work  any  instrument  of  the  wet  and  dry  bulb  type 
should  be  used  in  a  current  of  air  of  not  less  than  15  feet  per  second. 

12.  For  Close  Approximation*  and  to  avoid  calculations, 
the  humidity  chart,  Fig.  7,  may  also  be  used  in  determining 
relative  humidity,  absolute  humidity,  dew  point,  temperature 
of  wet  bulb  and  temperature  of  dry  bulb.  On  the  left  of  the 
chart  is  a  scale  referring  to  horizontal  lines  giving  tempera- 
tures of  the  wet  bulb.  The  scale  on  the  right  hand,  referring 
to  the  lines  curving  downward  from  right  to  left,  is  the  scale 
of  the  room,  or  dry  bulb,  temperatures.  The  scale  along  the 
bottom  of  the  chart  is  one  of  relative  humidity.  The  scale  of 
numbers  up  the  center  of  the  chart  refers  to  the  lines  curving 
downward  from  left  to  right,  and  indicates  the  absolute  hu- 
midity, i.  e.,  grains  of  moisture  per  cubic  foot  with  the  air. 
The  use  of  the  chart  may  be  most  readily  understood  by  a 
few  applications. 

APPLICATION.  —  Given  dry  bulb  70  degrees  and  wet  bulb  60 
degrees.  Determine  relative  humidity,  absolute  humidity, 
temperature  of  dew  point  for  room,  etc.  First,  starting  on 
the  right  hand  scale  at  70,  follow  down  the  line  this  number 
refers  to  until  it  crosses  the  horizontal  line  of  60  degrees, 
wet  bulb  temperature.  From  this  intersection  drop  to  the 
relative  humidity  scale  and  read  there  55  per  cent.  This  may 
be  checked  with  the  table.  To  obtain  the  absolute  humidity 
will  be  noticed  that  the  intersection  of  the  70  degree  and 

C-  o  o  >•<//'  5  i  ?  £~e-  5  -4"  -4 

degree-4+tt4»s  shows  -8  grains  per  cubic  foot.     If  the  room 


should  cool,  the  absolute  humidity  would  remain  the  same 
until  the  dew  point  is  reached  (neglecting  air  contraction), 
hence,  following  down  the  8  Wrain  line  to  100  per  cent,  gives 
the  room  temperature  as  ^*lr  degrees,  showing  that  if  so 
cooled  the  air  would  begin  depositing  moisture  at  this  tem- 
perature. Again  if  the  room  should  heat  to,  say,  90  degrees, 
the  relative  humidity  may  be  obtained  by  following  the  -#• 


26 


HEATING  AND  VENTILATION 


HYGROMETRIC    CHART 

OIVINO 

HYGROMETER  TEMPERATURES.  RELATIVE  HUMIDITY'. 'GRAINS  OF  MOISTURE  PER  CU.  FT. 


0          10         20        30        40        60        60        70        80-90       100 

RELATIVE  HUMIDITY  IN  t>ER  CENT 

Fig.  7. 


HUMIDIFYING   THE   AIR  27 

<2*>ord  t  >i  a<f 

grain  line  to  its  intersection  with  the  90  degree^  line  of 
room  temperature,  and  from  this  intersection  dropping  to  the 
relative  humidity  scale,  and  reading  there  8*- per  cent.  Thus, 
having  given  air  under  any  set  of  conditions,  the  effect  that 
a  change  in  any  one  of  these  would  have  upon  the  remaining 
may  be  obtained  without  calculations. 

13.  The  Theoretical  Amount  of  Moisture  to  be  Added  to 
Air  ao  as  to  Maintain  a  Certain  Humidity: — Warm  air  has  a 
much  greater  capacity  for  holding  moisture  than  cold  air. 
According  to  the  law  of  Gay-Lussac,  when  air  is  taken 
at  a  given  outside  temperature  and  heated  for  interior 
service,  the  volume  increases  with  the  absolute  tempera- 
ture. See  Art.  4.  On  the  other  hand  the  humidity  de- 
creases rapidly.  Air  thus  treated  becomes  dry  and  unpleas- 
ant to  the  occupants,  as  well  as  being  detrimental  to  the 
furnishings  of  the  room.  Some  means  should,  therefore,  be 
provided  to  supply  this  moisture  to  the  air  current. 

In  calculating  the  amount  to  be  added,  let  Q  =  volume 
of  air  in  cubic  feet  per  hour  entering  the  room  at  the  reg- 
ister; t  =  its  temperature  in  degrees  and  T  =  (460  +  t)  = 
its  absolute  temperature;  let  Q'  and  Qo  —  the  correspond- 
ing volumes  after  entering  and  before  entering,  with 
t'  and  to  the  temperatures  in  degrees,  and  T'  =  (460  +  V) 
and  To  =•  (460  +  to)  the  absolute  temperatures;  also,  let  u' 
and  Uo  be  the  humidities,  respectively,  of  the  room  air  and 
the  outside  air.  Then,  from  the  equations 

TQ'  =  T'Q  and  TQQ  —  T0Q  (4) 

find  Q'  and  Q0. 

From  Table  9,  Appendix,  find  the  amounts  of  moisture 
Ai'  and  M0  in  one  cubic  foot  of  saturated  air  at  the  temper- 
atures t'  and  t0;  multiply  these  by  the  respective  humidities 
and  volumes,  and  the  difference  between  the  two  final  quan- 
tities will  be  the  amount  of  moisture  required  per  hour  as 
expressed  by  the  formula, 

W  =  Q'M'u'  —  QQM0ii0  (5) 

APPLICATION. — Let  Q  —  5000,  t  —  130,  t'  —  70,  to  =  30,  u'  — 
.50,  u0  —  .50,   M'  —   7.98,   and  Jf0  —   1.958,    then 
Q'  =  5000   X   530  -h  590  —  4490 
Q0  —  5000   X   490  -e-  590  =  4154 
W  =  13867  grains,  or  1.984  pounds  per  hour. 
This  means  that  approximately  2  pounds  of  water  would  be 
evaporated  for   every  5000   cubic   feet  of  fresh   air   entering 
the  register  under  the  above   conditions. 


HEATING  AND  VENTILATION 


14.  Velocity  in  the  Convection  of  Air  by  the  Applica- 
tion of  Heat: — Let  7;0  Fig.  8,  be  the  height  of  the  chimney 
£•  or  stack.  If  the  temperature  of  the  gases 
within  the  chimney  CD  be  the  same  as  that 
of  the  entering  air,  then  there  will  be  no 
0  natural  circulation,  because  the  column,  CD, 
will  just  balance  a  corresponding  column 
AB  upon  the  outside;  but  if  the  temperature 
of  the  chimney  gases  CD  and  entering  air 
4.B  be  tc  degrees  and  to  degrees,  respectively, 
the  chimney  gases  being  (tc  --  to)  degrees 
greater  than  that  of  the  outside  air,  then, 
upon  entering  the  chimney,  the  gases  will 
become  less  dense  and  expand  an  amount 
proportional  to  the  absolute  temperature. 
With  an  outside  column  of  ho  feet  in  height, 
it  will  then  require  a  column  within,  ho  +  ho 
feet  in  height  to  produce  equilibrium;  in  oth- 
C  er  words,  the  column  of  gas  producing  mo- 
tion in  the  chimney  has  a  height  of  he  feet. 
Assume,  in  the  system  of  ABCDE,  that  the 
cross  sections  at  all  points  be  uniform,  then  the  volumes  of 
AB  (imaginary  column)  and  CE  (actual  column)  are  to 
each  other  as  their  respective  heights,  i.  e., 
Vo  :  To  +  V°  :  :ho  :  ho  +  /»c,  and  ho  :  460  +  to  :  :  lio  +  ho  :  460  -f  tc 
From  this  we  obtain  he  (460  +  to)  =  ho  (tc  —  to)  and 


Fig.   8. 


ho    (to   —  to) 


(6) 


460  +  to 

Substituting  for  h  in  the  equation  v  —  V2  yh,  its  correspond- 
ing value  he,  we  have 


v  =  V  2ghe  =  8.02 


V 


(tc    —    to) 


(7) 


460  +  to 

It  is  found  in  practice  that  the  theoretical  velocity  as 
given  by  this  formula  is  never  obtained,  because  of  the 
friction  of  the  sides  of  the  chimney  and  other  causes.  Mr. 
Alfred  R.  Wolff  quoted  the  actual  discharge  from  the  chim- 
ney as  50  per  cent,  of  the  theoretical.  This  estimate  may 
be  fairly  correct  for  chimneys  of  the  larger  sizes,  but  may 
not  be  realized  on  the  smaller  ones  used  in  residences.  As 
the  transverse  area  becomes  smaller,  the  percentage  of  fric- 
tion increases  very  rapidly  and  soon  becomes  the  principal 


MEASUREMENT  OF  AIR  VELOCITIES  29 

factor.  Prof.  Kent  assumes  a  layer  of  gas  two  inches  thick 
next  the  interior  surface  as  being  ineffective.  This,  if  ap- 
plied to  small  cross-sectional  areas,  increases  the  size  of 
the  chimney  rapidly  from  the  calculated  amount. 

When  formula  7  is  applied  to  hot  air  stacks  in  the 
heating1  systems,  the  friction  is  much  less  because  of  the 
smooth  interior,  and  the  actual  velocity  of  the  air  should 
reach  60  to  70  per  cent,  of  the  theoretical. 

15.  Measurement  of  Air  Velocities: — See  also  Art.  115. 
In  ventilating  work  it  is  often  of  the  greatest  importance 
to  determine  air  velocities  accurately.  The  correct  deter- 
mination of  the  sizes  of  air  propelling  fans  or  blowers 
depends  upon  the  ability  to  accurately  measure  the  /velocity 
of  delivery.  In  acceptance  and  other  tests  this  measurement 
is  equally  important.  However,  no  entirely  satisfactory  and 
trustworthy  method  of  obtaining  this  measurement  has  as 
yet  been  devised. 

The  velocity  of  moving  air  is  most  commonly  measured 
by  means  of  a  vane  w'heel  instrument  called  the  anemometer. 
It  consists  essentially  of  a  delicately  pivoted  wheel  holding 
from  6  to  15  vanes  and  similar  to  the  common  wind-mill 
w.heel.  See  Fig.  9.  To  the  shaft  is  connected  a  recording 
mechanism  of  some  sort,  the  simplest 
being  merely  dials  which  show  the 
velocity  of  the  air  traveling  past  the 
instrument,  by  the  reading  of  which 
against  a  stop-watch,  the  speed  per 
unit  of  time  may  be  obtained.  Since 
the  instrument  works  against  the 
friction  of  moving  parts,  its  readings 
are  subject  to  serious  variation,  and 
even  with  frequent  calibration,  it  is 
not  to  be  relied  upon  where  results 
are  required  accurate  to  within  20 
Fig.  9.  per  cent.  Various  tests  of  anemom- 

eters   by    comparison    to    the    absolute 

readings  of  a  gas  tank  have  shown  errors  as  high  as  35 
per  cent,  slow,  to  14  per  cent,  fast,  with  the  discharge  from 
pipes  8  inches  to  24  inches  in  diameter.  Hence,  in  general, 
it  is  very  safe  to  say  that  the  anemometer  as  an  instrument 
for  velocity  measurement  in  precise  work  should  be  used 
with  great  care. 


30 


HEATING  AND  VENTILATION 


A  second  method  of  velocity  measurement,  and  on'3 
applying  as  readily  to  liquids  as  to  gases,  is  that  of  using- 
the  Pitot  tube  principle.  Whenever,  in  a  liquid  or  gas,  a 
pressure  produces  a  flow,  part  of  this  pressure,  usually 
termed  the  velocity  head,  is  considered  as  transformed  into 
velocity;  while  a  second  part,  usually  called  the  pressure 
head,  acts  to  produce  pressure  in  the  fluid.  If  now,  as  at 
A,  in  Fig.  10,  a  tube  be  inserted  into  a  pipe  carrying  a 


B 


Fig.   10. 

current  of  air  or  other  moving  fluid,  and  the  end  of  this 
tube  be  bent  so  the  plane  of  the  opening  is  perpendicular 
to  the  direction  of  the  flow,  a  pressure  in  the  tube  will 
result,  due  to  both  the  velocity  head  and  the  pressure  head; 
and  the  difference  in  levels  in  the  connected  manometer 
tube  will  indicate  this  sum  of  pressures  in  terms  of  inches 
of  water  or  mercury.  If,  however,  a  tube  be  inserted  as  at 
B,  with  the  plane  of  its  opening  parallel  to  the  direction 
of  the  flow,  a  pressure  in  the  tube  will  result,  due  only 
to  the  pressure  head  in  the  moving  fluid;  and  the  difference 
in  levels  in  the  connected  manometer  tube  will  indicate  this 
pressure  only.  Then,  by  subtraction  of  the  two  manom- 
eter readings,  the  velocity  head  only  is  obtained,  expressed 
in  inches  of  water  or  mercury,  whichever  the  manometer 
may  contain. 

At  C  is  shown  the  instrument  as  commonly  applied, 
with  both  tubes  together  and  connected  one  to  either  leg 
of  the  manometer  tube  so  that  the  subtraction  is  automatic, 
and  the  difference  in  levels  read  is  caused  by  the  velocity 
only.  Having,  then,  the  head  of  pressure  due  to  velocity, 
to  find  the  actual  velocity  apply  the  formula  v  =  ^/2gJT  where 
v  —  velocity  in  feet  per  second,  g  =  acceleration  of  gravity 
in  feet  per  second,  per  second,  and  h  =  the  velocity  head 
of  the  air  in  feet.  If  the  manometer  contains  water,  then, 


PITOT  TUBE  31 


at  60   degrees,  the  ratio  between  the   specific  gravity  of  air 

62.37 

and  water  is  — =  816.4.    See  Tables  9  and  6,  Appendix. 

.0764 

Hence  the  above  formula  may  be  reduced  to  the  more  read- 
ily  available   form  of 


v  =.J   2   X   32.16  X   816.4  X  ,  or 

12 


0=  66.2  V7^T~  (8) 

where  hw  =  the  difference  in  height  in  inches  of  the  columns 
of  a  water  manometer,  with  both  legs  connected  as  described, 
and  a  temperature  of  60  degrees.  By  a  similar  method  the 
formula  may  be  reduced  for  a  mercury  or  other  manometer, 
or  for  other  temperatures  than  60  degrees. 

In  using  the  Pitot  tube  or  the  anemometer,  the  fact 
should  not  be  lost  sight  of  that  the  velocity  varies  from 
a  minimum  at  the  inner  walls  of  the  tube  to  the  maximum 
at  the  center  of  the  tube.  It  seems  that  the  friction  at  the 
inner  walls  throws  the  moving  fluid  into  a  number  of 
concentric  layers,  those  toward  the  center  moving  the  fast- 
est, those  toward  the  inner  wall  of  the  pipe  the  slowest. 
With  a  circular  tube,  the  variation  of  velocities  of  these 
different  layers  may  be  approximately  represented  by  the 
abscissae  of  a  parabola,  Fig.  11,  with  its  axis  on  the  axis  of 
the  circular  pipe.  Weisbach,  on  page  189  of  his  Mechanics  of 


Fig.   11. 

Air  Machinery,  quotes  the  average  speed  at  two-thirds  of  the 
radius  from  the  center,  this  value  being  obtained  by  ex- 
periments. For  conduits  of  other  shapes  the  position  of 
mean  velocity  must  be  determined  experimentally.  This 
variation  of  velocity  from  the  center  of  the  stream  less- 


32  HEATING  AND  VENTILATION 

ening  toward  the  walls  may  possibly  account  for  the  vari- 
ations shown  by  the  anemometers.  It  is  evident  that 
if  such  an  instrument,  with  a  given  diameter  of  vane 
wheel,  be  placed  at  the  center  of  a  pipe  of  large  radius  it 
would  tend  to  register  a  higher  velocity  than  the  average. 

1C.  Amount  of  Air  Required  to  Burn  Carbon: — The  chief 
product  in  the  combustion  of  carbon  with  the  oxygen  of  the 
air  is  CO^.  The  atomic  weight  of  carbon  is  12  and  that 
of  oxygen  is  16,  hence  the  chemical  union  of  the  two  form- 
ing CO2  is  in  the  proportion  of  carbon  12  and  oxygen  32 
or  as  1  :  2.66.  For  each  pound  of  carbon  consumed,  2.66 
pounds  of  oxygen  will  be  needed  and  the  product  will  weigh 
3.66  pounds.  If  pure  air  contains  23  per  cent,  oxygen,  then 
one  pound  of  carbon  will  need  2.66  ~  .23  =  11.7,  say  12 
pounds  of  air  for  complete  combustion.  One  cubic  foot 
of  air  at  32  degrees  weighs  .0807  pounds,  then  12  -^-  .0807  — 
148  cubic  feet  of  air  necessary  to  burn  one  pound  of  car- 
bon if  all  the  oxygen  of  the  air  is  burned.  With  volumes 
proportional  to  the  absolute  temperatures,  this  air  at  70 
degrees  would  be  160  cubic  feet;  at  200  degrees,  200  cubic 
feet;  at  400  degrees,  260  cubic  feet;  and  at  600  degrees,  320 
cubic  feet. 

17.  Probable  Amount  of  Air  Used: — It  seems  reason- 
able to  assume,  however,  that  in  practice  from  two  to 
three  times  as  much  air  goes  through  a  furnace  as  would 
be  needed  for  perfect  combustion.  Taking  this  at,  say,  2.5, 
then  the  cubic  feet  of  air  found  from  tfce  above  would  be 
approximately:  32  degrees,  370  cubic  feet;  70  degrees,  400 
cubic  feet;  200  degrees,  500  cubic  feet;  400  degrees,  650  cubic 
feet;  and  600  degrees,  800  cubic  feet. 

IS.  To  Determine  the  Transverse  Area  of  a  Chimney 
for  Any  Given  Height: — Substitute  ho  and  the  assumed 
values  of  tc  and  to  in  formula  7,  Art.  14.  f  rom  this  find 
the  velocity  of  the  chimney  gases,  and  divide  the  total 
volume  of  air  used  in  any  given  time,  Art.  17,  by  the 
corresponding  velocity. 

10.  Application  to  the  Chimney  of  a  10  Room  Resi- 
dence:— Given:  total  heat  loss  from  the  building  per  hour, 
100000  B.  t.  u.;  coal  13500  B.  t.  u.  per  pound;  furnace 
efficiency,  60  per  cent;  temperature  at  bottom  of  chimney, 
200  degrees  F.;  height  of  chimney,  30  feet  above  the  grate; 
average  temperature  of  chimney  gases,  150  degrees.  (The 


CHIMNEYS.  33 

greatest  difficulty  is  experienced  when  the  fire  is  first 
started  before  the  chimney  is  warmed  up.  The  temperature 
of  the  stack  gases  at  such  a  time  is  very  low.)  Take  the 
outside  air  temperature,  40  degrees  P.,  and  find  the  size  of 
the  chimney. 

A  heat  loss  of  100000  B.  t.  u.  per  hour  will  require 
100000  -~  (13500  X  .60)  =  12.4  pounds  of  coal  per  hour  at 
the  grate;  then  with  a  temperature  of  200  degrees  at  the 
bottom  of  the  chimney,  this  will  need  to  pass  500  X  12.4  = 
6200  cubic  feet  of  air  per  hour.  The  velocity  of  the  chim- 
ney gases,  according  to  formula,  is  20.5  feet  per  second  or 
73800  feet  per  hour.  Assuming  the  real  velocity  to  be,  say, 
25  per  cent,  of  this  amount,  we  have  approximately  18450 
feet  per  hour;  then  the  net  sectional  area  is  6200  -i-  18450 
=  .34  square  foot  or  49  square  inches.  To  fit  the  brick 
work  this  would  probably  be  made  8  inches  X  8  inches. 

20.  All  Chimneys  should  have  a  Smooth  Finish  on  the 
Inside: — Probably  the  best  arrangement  that  can  be  made 
is  to  build  the  chimney  of  hard  burned  brick  around  hard 
burned  tiles  of  suitable  internal  size.  These  tiles  can  be 
had  of  outside  sizes  such  that  they  can  easily  be  made  to 
work  in  with  the  brick  work.  Table  12,  Appendix,  shows 
chimney  capacities  that  will  be  safe  in  average  practice. 
Flues  should  preferably  be  made  round  in  section,  as  this 
form  presents  less  friction  to  the  gases  than  any  other. 
B  lues  should  never  be  built  less  than  ten  inches  in  diam- 
eter, or  eight  by  ten  inches  rectangular.  The  value  of  a 
flue  depends  very  much  upon  the  volume  of  passage  due 
to  area,  and  velocity  due  to  height.  Velocity  alone  is  no 
proof  of  good  draft  for  there  must  also  be  sufficient  area 
to  carry  the  smoke.  The  top  of  a  chimney  with  reference 
to  its  position  relative  to  neighboring  structures  is  a  very 
important  consideration.  If  the  top  is  below  any  nearby 
portion  of  the  building,  eddy  currents  tending  to  enter  the 
top  of  the  flue  may  be  formed  and  seriously  reduce  the  draft. 
Under  such  conditions  a  shifting  cowl,  which  always  turns 
the  outlet  away  from  adverse  currents,  may  be  advisable. 
Good  draft  Is  very  essential  to  the  success  of  any  type  of 
heating  system,  and  the  purchaser  of  a  furnace  or  heater 
should  be  required  to  guarantee  sufficient  draft  before  a 
maker  is  expected  to  guarantee  a  stated  rating  of  his 
furnace  or  heater. 


34  HEATING  AND  VENTILATION 


REFERENCES. 

References    on   Ventilation    and    the    Air    Supply. 

TECHNICAL  BOOKS. 

Moore,  The  School  House,  p.  24.  Monroe,  Steam  Heat.  &  Vent., 
p.  99.  Carpenter,  Heat.  &  Vent.  Bldgs.,  p.  21.  Hubbard,  Power, 
Heat.  &  Vent.,  p.  408.  Allen,  Notes  on  Heat.  &  Vent.,  p.  91 
Ency.  Brit.,  Vol.  XXIV,  p.  157,  also  Vol.  XX,  p.  474. 

TECHNICAL     PERIODICALS. 

Engr.  Rev.,  Sanitation  and  Ventilation  in  Boston  School 
Houses,  W.  B.  Snow,  March,  1908,  p.  15.  Subway  Ventilation, 
J.  B.  Holbrook,  Jan.  1905,  p.  18.  Ventilation  of  School  Rooms, 
Nov.  1905,  p.  6.  Heat.  &  Vent.  Magazine.  A  Scotchman's  Notes  on 
Ventilation,  Alex.  Mackenzie,  May  1906,  p.  15.  Air  Analysis  as 
an  Aid  to  the  Ventilating  Engineer,  J.  R.  Preston,  Oct.  1906,  p. 
11.  Domestic  Engineering.  Ventilation  in  its  Relation  to  Health, 
W.  G.  Snow,  Vol.  52,  No.  4,  July  23,  1910,  p.  102;  Vol.  52,  No.  6, 
Aug.  6,  1910,  p.  154.  Ventilation  of  Isolated  Offices,  C.  L. 
Hubbard,  Vol.  45,  No.  10,  Dec.  5,  1908,  p.  274.  Trans.  A.  S.  H. 
d  V.  E.  The  Necessity  of  Moisture  in  Heated  Houses,  R.  C.  Car- 
penter, Vol.  X,  p.  129.  Need  of  Ventilation  in  Heated  Build- 
ings, Vol.  X,  p.  183.  Changing  the  Air  in  a  Room,  Vol.  X.  p. 
285.  Effect  of  Humidity  on  Heating  Systems,  Vol.  IX,  p.  323. 
Necessity  of  Ventilation,  H.  Eisert,  Vol.  V.  p.  57.  The  Engin- 
eering Magazine.  Humidifiers, — Their  Principles  and  Useful  Ap- 
plications, S.  H.  Bunnell,  June  1910.  The  Heating,  Ventilating 
and  Air  Conditions  of  Factories.  P.  R.  Moses,  Aug.  and 
Sept.  1910. 


CHAPTER   III. 


HEAT  LOSSES  FROM  BUILDINGS. 


21.      Loss    of    Heat    by    Conduction    and    Radiation: — In 

planning  the  heating  system  for  any  building,  the  first,  and 
probably  the  most  important,  part  of  the  work  is  to  esti- 
mate the  total  heat  loss  per  hour  from  the  building.  Un- 
fortunately this  is  the  part  which  is  the  least  open  to 
satisfactory  calculations  and  we  find  little  valuable  theo- 
retical data  upon  the  subject 

Heat  is  lost  from  a  building  in  two  ways,  by  radiation 
and  by  convection,  i.  e.,  that  transferred  through  walls,  win- 
dows and  other  exposed  surfaces  by  conduction  and  lost 
by  radiation;  and  that  carried  off  by  the  movement  of  the 
air  as  it  passes  out  through  the  openings  in  the  building 
to  the  outside  air.  The  radiation  loss  is  usually  of  greater 
importance,  but  the  convection  loss  is  of  much  more  im- 
portance than  is  generally  considered.  In  the  average 
building  both  of  these  values  are  difficult  to  determine. 

Radiation  losses  are  considered  under  various  heads, 
such  as  glass,  wall,  floor,  ceiling  and  door  losses.  Concern- 
ing the  conduction  of  heat  through  these  various  materials, 
the  available  data  have  been  obtained  by  experimentation 
and  do  not  agree  very  closely.  Peclet  in  France,  and  Gras- 
hof,  Rietschel,  Klinger  and  Rechnagel  in  Germany,  each 
carried  on  experimental  research  to  determine  the  heat 
transmission  through  various  materials  and  structures. 
These  published  data  form  the  basis  for  a  large  part  of  the 
heat  loss  calculations  of  the  present  time.  Much  valuable 
material  can  be  found  in  the  more  recent  writings  of 
Hood,  Wolff,  Box,  Carpenter,  Kinealy,  Allen,  Hogan,  Hub- 
bard  and  others,  but  many  of  the  values  quoted  are  only 
rough  approximations  at  best.  The  reason  for  so  much 
uncertainty  in  this  part  of  the  work  is  found  in  the  fact 
that  there  are  such  great  differences  in  methods  of  build- 
ing construction.  Conductivity  tests  for  the  various  ma- 
terials have  been  satisfactorily  made,  but  when  these  same 
materials  have  been  put  into  a  building  wall  the  quality 
of  the  workmanship  often  permits  more  heat  loss  by  con- 


36  HEATING  AND  VENTILATION 

vection  than  would  be  transmitted  through  the  materials 
themselves.  The  values  quoted  for  brick  walls  and  glass 
agree  fairly  well.  The  greatest  difficulty  is  found  in  the 
balloon-framed  building  with  its  studded  walls,  where  the 
dead  air  space  in  a  well  constructed  wall  may  be  a  good 
non-conductor,  or  where,  on  the  other  hand,  the  same  space 
in  a  poorly  constructed  wall  may  become  a  circulating  air 
space  to  cool  the  walls  by  the  movement  of  the  air. 

Table  IV  has  been  compiled  from  a  number  of  the 
best  references  as  stated  above,  and  represents  a  fair  aver- 
age of  all  of  them.  The  value  K  (rate  of  transmission),  in 
some  of  the  references,  varied  for  the  same  material,  being 
somewhat  greater  for  small  temperature  differences  than 
where  the  temperatures  differed  widely.  Theoretically,  the 
transfer  of  heat  through  any  substance  is  directly  propor- 
tional to  the  difference  of  the  temperature  between  the  two 
sides  of  the  substance.  This  was  noticeably  true  for  most 
of  the  quotations. 

TABLE    IV. 

Conductivities   of  Building  Materials. 
K  =  B.  t.  u.  transmitted  per  sq.  ft.  per  hour  per  degree  dif. 

Materials.  K. 

Brick    Wall,      8", 4 

Brick    Wall,    12", .31 

Brick   Wall,    16", 26 

Brick   Wall,    20" 23 

Brick   Wall,    24", 21 

Brick    Wall    28", 19 

Brick   Wall,    32", 17 

Brick  Wall,  Furred,  use  .7  times  non-furred  in  each  case. 
Stone  Wall,  Use  1.5  times  brick  wall  in  each  case. 

Windows,     Single    Glass, 1.0 

Windows,     Double    Glass,    6 

Skylight,      Single    Glass, 1.1 

Skylight,      Double  Glass,   7 

Wooden  Door,   1", 4 

Wooden   Door,   2", 36 

Solid  Plaster  Partition,   2", 6 

Solid  Plaster  Partition,   3", 6 

Ordinary  Stud  Partition,  Lath  and  Plaster  on  one  side      .6 


HEAT  LOSSES  FROM  BUILDINGS  37 

Ordinary  Stud  Partition,  Lath  and  Plaster  on  two  sides     .34 

Concrete  Floor  on  Brick  Arch, 2 

Fireproof  Construction  as  Flooring,. 1 

Fireproof  Construction  as  Ceiling, 14 

Single   Wood  Floor  on  Brick  Arch 15 

Double    Wood    Floor,    Plaster    beneath, 10 

Wooden   Beams   planked    over,    as   Flooring, 17 

Wooden    Beams    planked    over,    as    Ceiling, 35 

Walls  of  the  Average  Wooden  Dwelling, 30 

Lath  and  Plaster  Ceiling,   no  floor  above, 62 

Lath  and  Plaster  Ceiling,  floor  above, 25 

Steel    Ceilings,  with   floor   above, 35 

Single  %"  Floor,  no  plaster  beneath, 45 

Single  %"  Floor,  Plaster  beneath, 26 

The  following  equivalents  for  doors,  floors  and  ceilings 
have  been  found  to  give  good  results: 

Doors  not  protected  by  storm  doors  or  vestibule  =  200%  of 
equal  wall  area. 

Floor  over  unheated  space.  Air  circulation  =  same  as  wall. 
Floor  over  unheated  space.  Still  air  =  40%  of  equal  wall  area. 
Ceiling  below  unheated  space.  Air  circulation  =  125%  of 
equal  wall  area. 

Ceiling  below  unheated  space.  Still  air  =  50%  of  equal  wall 
area. 

In  all  references  from  French  and  German  authorities, 
one  is  impressed  by  the  extreme  care  and  exactness  with 
which  every  detail  is  worked  out,  even  to  those  minor  parts 
usually  considered  in  this  country  of  no  special  moment. 

22.  Loss  of  Heat  by  Air  Leakage: — The  exact  amount 
of  air  leaving  a  building  by  leakage  is  impossible  to  de- 
termine. Many  experiments  have  been  carried  on  in  the 
last  few  years  to  determine  the  amount  of  leakage  around 
windows  and  doors.  These  in  the  specific  cases  have  been 
successful,  but  no  actual  values  can  be  quoted  for  general 
use.  Again,  a  considerable  amount  of  air  passes  through 
the  walls,  thus  rendering  the  case  more  complicated.  In  all 
the  experiments,  however,  it  has  been  found  that  these 
losses  have  been  much  greater  than  was  supposed.  In 
rooms  not  heavily  exposed,  or  in  touch  with  heavy  winds, 
two  changes  per  hour  may  be  safely  allowed  for  all  leakage 
losses. 


38  HEATING  AND  VENTILATION 

23.  Exposure     Losses     and     Other     Losses: — Radiation 
losses  are  much  greater  on  the  exposed  or  windward  side  of 
the   building.   Moving   air   passing   over   the   surface   of   any 
radiating  material  will  wipe  the  heat  off  faster  than  would 
be  true  of  still  air.     The  north,  north-west  and  the  north- 
east in  most  sections  of  the  country  get  the  highest  winds 
and    have    the    least    benefit    of    the    sun    and   are    therefore 
counted   the   cold   portions   of   the   building.      In    figuring    a 
building  it   is  customary  to   figure   each  room  as   though   it 
were  a  south  room,  which  is  assumed  to  need  no  additions 
for    exposure,    and    then    add    a    certain    percentage    of    this 
loss  for  exposure  to  fit  the  location  of  the  room.     The  exact 
amount  to  add  in  each  case  is  largely  a  matter  of  the  judg- 
ment of  the  designer,  who,   of  course,  is  supposed  to  know 
the    direction   of   the    heavy   winds   and   the   protection   that 
is   afforded   by   surrounding   buildings.     A   wide    variety    of 
values  covering  the  American  practice  might  be  quoted  for 
this,   but   the   following  will   give   satisfactory   results: 

TABLE    V. 

North,    north-east    and    north-west    rooms    heavily    exposed, 

10-20  per  cent. 

East  or  west  rooms   moderately   exposed,....   5-10  per  cent. 

Rooms  heated  only  periodically, 20-40  per  cent. 

The   German   practice    is    somewhat   more   extreme   than 

ours  in  this  part  of  the  work: 

North,   north-east  and  north-west  rooms  heavily  exposed, 

15-25  per  cent. 

East    and    west    rooms, 10-15  per  cent. 

Surfaces  exposed  to  heavy  winds, 10-20  per  cent. 

Heat  interrupted  daily  but  rooms  kept  closed       10  per  cent. 

Heat  interrupted  daily  but  rooms  kept  opened       30  per  cent. 

Heat  off  for  long  periods 50  per  cent. 

Rooms  12  to  14%  feet  from  floor  to  ceiling,..          3  per  cent. 

Rooms  14%  to  18  feet  from  floor  to  ceiling,..          6  per  cent. 

Rooms  18  feet  and  above  from  floor  to  ceiling       10  per  cent. 

24.  Loss  of  Heat  by  Ventilation: — A  certain  amount  of 
fresh  air  leaks  into  every   building  and  displaces  an  equal 
amount  of  warm  air,  but  this  amount  of  fresh  leakage  air 
is    not    considered    sufficient    for    good    ventilation.      When 
warm  air  is  displaced  either  by  leakage  or  by  ventilation, 


ESTIMATION  OF  HEAT  LOSS  39 

it  is  exhausted  to  the  outside  air  and  as  it  leaves  the  room 
carries  a  certain  amount  of  heat  with  it.  This  is  a  direct 
loss  and  should  be  taken  into  account. 

Since  the  loss  by  leakage  is  practically  the  same  for 
all  systems  of  heating,  it  is  accounted  for  in  the  ordinary 
heat  loss  formula,  but  losses  by  ventilating  systems  must 
be  considered  in  excess  of  this  amount.  Let  Q'  =  cubic  feet 
of  fresh  air  supplied  per  hour,  V  —  to  =  drop  in  temperature 
from  the  inside  to  the  outside  air;  then  the  heat  lost  by  ex- 
hausting the  air,  Art.  27,  is 

Q'   (tf  —  to) 


« 
55 

25.  Two  General  Methods  of  Estimating  the  Heat  Loss  H 
from   a   Building   are   in   Common   Use:  —  First,    estimate    all 
radiation  losses   and   add  to   their   sum  a   certain   per  cent. 
of  itself  to  allow  for  leakage  by   convection;    second,   esti- 
mate   all    radiation   losses   and  add   to   their   sum   a  certain 
amount  which   depends   upon  the   volume   of   the   room.   The 
first  is  by  Equivalent  Radiating  Surfaces  only  and  the  second  is 
by  Equivalent  Radiating  Surfaces  and  Volume  combined. 

26.  Method  No.   1:  —  Figuring  by   Equivalent  Radiating 
Surface.  —  Let  H  =  R,   t.    u.   heat  loss   from  room  per  hour; 
G  =  exposed  glass  in  square  feet;  W  =  exposed  wall  minus 
glass  plus  exposed  doors  reduced  to  equivalent  wall  surface 
in  square  feet;  F  =  floor  or  ceiling  separating  warm  room 
from  unheated  space;  tx  =  difference  between  room  temper- 
ature   and    outside    temperature;    ty    =    difference    between 
room   temperature  and  temperature   of  the  unheated  space; 
K,  K'  and  K"  =  coefficients   of  heat  transmission;   a  =  per- 
centage  allowed   for  exposure   and  &  =  percentage   allowed 
for   loss    by   leakage,    varying    in   per   cent,    of    other   losses 
from   10    in   the   average   house  to   30   in  the  house   of  poor 
construction. 

From  the   above,   we   have 

H  =  (KGt,  +  K'Wtm  +  K"Fty)    (!  +  «+&)  (10) 

APPLICATION.—  Assume  the  sitting  room,  Fig.  14,  to  have 
a  total  exposed  wall  surface,  W,  exclusive  of  glass,  242 
square  feet;  total  exposed  glass,  (?,  38  square  feet;  and 


40  HEATING  AND  VENTILATION 

floor,  F,  195  square  feet.  Assume  that  all  the  rooms  are 
heated  to  70  degrees  with  an  outside  temperature  of  zero 
degrees  and  that  all  workmanship  is  fair.  Assume  also  the 
floor  to  be  of  the  ordinary  thickness  and  not  ceiled  below,  with 
a  temperature  below  the  floor  of  this  room  of  32  degrees; 
and  that  two  people  are  using  the  room.  Under  such  con- 
ditions what  is  the  heat  loss  from  the  room?  Since  this 
is  a  south  room  there  is  no  exposure  loss  and  0  =  0.  Then 
assuming  6  =  .20  we  have 

H  =  (1  X  38  X  70  +  .3  X  242  X  70  +  .45  X  194X  38)  (1  +  .20) 
=  13270  B.  t.  u. 

27.     Method  No.  2: — Figuring  by  Equivalent   Radiating 
Surface  and  Volume. — The  general  formula  for  this  is 

H  =  (KGt*  +  K'Wt*  +  K"Ftv  +  ocnCfe)   (1  +  o)  (11) 

where  H,  K,  O,  tx,  tv,  W,  F  and  a  are  as  given  above;  C  =  cubic 
volume  of  the  room;  n  =  number  of  times  the  air  is  sup- 
posed to  change  in  the  room  by  leakage  and  convection  per 

hour,  recommended,  1  to  2;    oc  =  A-  and  is  usually  taken  .02 

55 
for  convenience  of  calculation.     This  constant  refers  to  the 

heat  carried  away  by  the  air.  The  specific  heat  of  the  air 
at  32  degrees  is  .238;  then  the  number  of  pounds  of  air 
heated  from  32  to  33  degrees  by  1  B.  t.  u.  is  1  -T-  .238  =  4.2. 
Now  if  the  weight  of  a  cubic  foot  of  air  at  32  degrees  is  .0807 
pounds,  we  would  have  4.2  -T-  .0807  =  52  cubic  feet  of  air 
heated  from  32  to  33  degrees  by  1  B.  t.  u.  However,  most 
of  the  heating  is  not  done  at  from  32  to  33  degrees  but 
from  32  to  70  degrees,  in  which  case,  the  volume  of  air 
heated  from  69  to  70  degrees  by  1  B.  t.  u.  is  52  X  530  -^ 
492  =  56  cubic  feet.  See  absolute  temperature,  Art.  4.  It 
is  evident  that  some  approximation  must  here  be  made.  No 
exact  value  can  be  taken  because  of  the  great  range  of 
temperature  change  of  the  air,  but  55  is  commonly  used 
as  the  best  average.  The  difficulty  of  handling  the  formula 

with  the  constant  -=-=-  has  led  to  the  simple  form,  .02. 

55 

APPLICATION. — With  the  same  room  as  used  in  Application 
1,  we  have,  if  o  =  0, 

&  =    (1    X    38    X   70   +    .3    X    242    X   70  +   .45  X  195  X  38  + 
.02  X  1  X  1950  X  70)  (1  +  0)  =  13806  B.  t.  u. 


ESTIMATION  OF  HEAT  LOSS  41 

28.  Method  No.   3: — Professor    Carpenter    reviews    the 
work    of    the    various    authors    and    quotes    the    following 
formula,   which  is  the  same  as  that  given  in  Method  No.   2 
in   a    more    simplified    form,    with    the    terms   the    same    as 
before: 

H  =  (Gf  +   .25  W  +  .02  nC)  t,  (12) 

In  his  opinion  the  very  elaborate  methods  sometimes  used 
are  unnecessary.  K  may  be  assumed  .25  for  any  ordinary 
wall  surface,  bricK  or  frame,  and  the  ceilings  adjoining  an 
attic  or  the  floors  above  a  cellar  of  the  average  house  need 
not  be  considered.  Floors  above  an  unexcavated  space 
where  no  heat  is  obtained  from  the  furnace  and  where  there 
is  more  or  less  circulation  of  air  should  no  doubt  have 
some  allowance.  This  would  probably  be  the  same  as  given 
in  Art.  21.  The  values  of  n  are  quoted  by  the  same  author- 
ity as  follows: 

Values  of  ro. 

Residence  Heating,  Halls,  3;  Sitting  room  and  rooms  on 
the  first  floor,  2;  Sleeping  rooms  and  rooms  on  second 
floor,  1. 

Stores,   First  floor,   2  to   3;   Second   floor,   1^  to   2. 

Offices,   First  floor,   2  to  2y2',   Second  floor,   1%  to   2. 

Churches    and   Public   Assembly   rooms,    %    to   2. 

Large  rooms   with   small   exposure,  ^  to   1. 

APPLICATION.- — Assuming  the   same   room  as  before, 
H  =  [38  +  .25  (242  +  .4  X  195)  +   .02  X  2  X  1950]  70  =  13720. 

29.  Combined  Heat  Loss  H'  =  (H  +  Hv) :— In  buildings 
where  ventilation  is  provided,  the  total  heat  loss  is  that  lost 
by  radiation,  H,  +  that  lost  by  ventilation,  Hr,  (see  also  Art.. 
36).    Letting   Qv   =   cubic   feet    of   air    needed    per    hour   for 
ventilation,    we   have, 

Qv  t* 

H'  =  H  H (13) 

5  o 

30.  Temperatures   to   be   Considered: — The   temperature 
maintained  in  heated  rooms   in.  this   country   is   70   degrees. 
Outside  temperatures  used  in  figuring  heat  losses  are  gen- 
erally taken,  southern  part,  +  10  degrees;   northern  part  — 
10  degrees;   ordinary  value,   0   degrees. 

The  German  Government  requires  estimates  on  the  fol- 
lowing temperatures,  as  quoted  in  "Formulas  and  Tables 
for  Heating,"  by  Prof.  J.  H.  Kinealy. 


42  HEATING  AND  VENTILATION 

TABLE  VI.— Values  of  t'. 


The    temperatures    of    heated    rooms    are    generally    as- 
sumed by  the  German  Engineers  to  be  as  follows: 

Rooms  in  which  the  occupants  are  for  the  most  part  at  rest: 
Living  rooms,  business   rooms,  court  houses,  offices, 

schools 68 

Lecture    halls    and    auditoriums -..61  to  64 

Rooms   used  only  as  sleeping  rooms 54  to  59 

Bath   rooms   in   dwellings 68  to  72 

Sick   rooms     72 

Rooms   in   which  the   occupants   are   undergoing   bodily   ex- 
ertion:' 
Workshops,  gymnasiums,  fencing  halls,  etc.,  in  which 

the  exertion  is  vigorous     50  to  59 

Workshops    in    which    the    exertion    is    not    so    vig- 
orous      61  to  64 

Rooms  used  as  passage  rooms  or  occupied  by  people  in 
street   dress: 

Entrance  halls,   passages,   corridors,  vestibules,   54  to  59 
Churches   , 50  to  54 

Miscellaneous: 

Prisons    for    the    confinement    of    prisoners    during 

the   day     64 

Prisons    for    the    confinement    of    prisoners    during 

the  night    50 

Hot  houses 77 

Cooling   houses     59 

Bath  houses: 

Swimming  halls   68 

Treatment  rooms,  massage  rooms 77 

Steam    bath      113 

Warm  air  bath    122 

Hot  air  bath     ,  ..140 


UNIVERSITY 

"""""tATION  OF  HEAT  LOSS  43 


TABLE  VII. 
Values  of  to  When  Applied  to  a  Room. 

The   temperatures    of    rooms   not   heated   are    quoted 
follows,  with  the  outside  air  at  4  degrees  below  zero: 

Cellars   and   rooms   kept  closed 32 

Rooms  often  in  communication  with  the  outside  air, 
such  as  passages,  entrance  halls,  vestibules,  etc.  23 
Attic    rooms    immediately    beneath    metal    or    slate 

roof     14 

Attic    rooms    immediately    beneath    tile,    cement,    or 
tar   and  gravel   roof 23 


31.  Heat  given  off  From  Lights  and  from  Persons 
"Within  the  Room: — As  a  credit  to  the  heating  system,  some 
heating  engineers  take  account  of  the  heat  radiated  from 
the  lights  and  the  persons  within  the  room.  The  following- 
table  by  Rubner  is  quoted  by  Prof.  Kinealy: 

TABLE  VIII. 

Gas,  ordinary  split  burner,  B.  t.  u.  per  candle  power  hr.  300 
Gas,  Argand  burner,     "  "  "         "  "       "       200 

Gas,  Auer  burner,         "  "  "         "  "       "         31 

Petroleum,  "  "  "       "       160 

Electric,   Incandesc't   "  "       "         14 

Electric,    Arc  "  "  "         "  "  4.3 

According  to  Pettenkofer,  the  mean  amount  of  heat 
given  off  per  person  per  hour  is  400  heat  units  for  adults 
and  200  for  children. 


44  HEATING  AND  VENTILATION 


REFERENCES. 

References  on  Heat  Losses  and  Radiation. 

TECHNICAL  BOOKS.    . 

iSnow,  Principles  of  Heat.,  p.  54.  Carpenter,  Heading  and 
Ventilating  Bldgs.,  p.  64.  Hubbard,  Power,  Heat,  and  Vent.,  p.  417. 
Allen,  Notes  on  Heat,  and  Vent.,  p.  13. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Air  Leakage  Around  Windows;  Its 
Prevention  and  Effects  on  Radiation,  Harold  McGeorge,  Feb. 
1910,  p.  64.  The  Heating  and  Ventilating  Magazine.  Austrian  Co- 
efficients for  the  Transmission  of  Heat  through  Building  Ma- 
terials, W.  W.  Macon,  Feb.  1908,  p.  36.  Air  Leakage  through 
Windows  and  its  Effect  Upon  the  AmJount  of  Radiation,  B. 
S.  Harrison,  Nov.  1907,  p.  18.  Air  Leakage  Around  Windows 
and  its  Prevention,  H.  W.  Whitten,  Dec.  1907,  p.  20.  Deriva- 
tion of  Constants  for  Building  Losses.  R.  C.  Carpenter, 
March  1907,  p.  34.  Methods  of  Estimating  Heat  Losses  from 
Buildings,  C.  L.  Hubbard,  Sept.  1907,  p.  1.  Trans.  A.  S.  H.  & 
V.  E.  Heat  Losses  and  Heat  Transmission,  Walter  Jones, 
Vol.  XII,  p.  234.  Loss  of  Heat  through  Walls  of  Buildings, 
R.  C.  Carpenter,  Vol.  VIII,  p.  94. 


CHAPTER   IV. 


FURNACE   HEATING   AND   VENTILATING. 


PRINCIPLES   OF  DESIGN. 

32.     Furnace   Systems   Compared   with   Other  Systems: — 

The  plan  of  heating  residences  and  other  small  buildings 
by  furnace  heat,  in  which  the  air  serves  as  a  heat  carrier,  is 
a  very  common  one  in  this  country.  Some  of  the  points  in 
favor  of  the  furnace  system  are:  low  cost  of  installation, 
heating  combined  with  ventilation,  and  the  rapidity  with 
which  the  system  responds  to  light  service  or  to  sudden 
changes  of  outdoor  temperatures.  Compared  with  that  of 
other  heating  systems,  the  furnace  system  can  be  installed 
for  one-third  to  one-half  the  cost.  In  addition  to  this,  the 
fact  that  ventilation  is  so  easily  obtained,  and  the  fact  that 
a  small  fire  on  a  mild  day  may  be  sufficient  to  remove  the 
chill  from  all  the  rooms,  give  this  method  of  heating  many 
advocates.  The  objections  to  the  system  are:  cost  of  operation 
when  outside  air  is  circulated,  difficulty  of  heating  the 
windward  side  of  the  house,  and  the  contamination  of  the 
air  supply  by  the  fuel  gases  leaking  through  the  joints  in 
the  furnace.  In  a  good  system  well  installed,  the  only 
objection  to  be  seriously  considered  is  the  difficulty  of  heat- 
ing that  part  of  the  house  subjected  to  the  pressure  of  the 
heavy  wind.  The  natural  draft  from  a  warm  air  furnace 
is  not  very  strong  at  best  and  any  differential  of  pressure 
in  the  various  rooms  will  tend  to  force  the  air  toward  the 
direction  of  least  resistance.  The  cost  of  operating  can  be 
controlled  to  the  satisfaction  of  the  owner  consistent  to  his 
ideas  of  the  quality  of  the  ventilation  needed.  Arrange- 
ments may  be  made  to  carry  the  warm  air  from  the  room 
back  again  to  the  furnace  to  be  reheated,  in  which  case, 
if  the  fresh  air  be  cut  off  entirely,  the  cost  of  heating  is 
about  the  same  as  that  of  any  system  of  direct  radiation 
having  no  provision  for  ventilation.  Any  amount  of  fresh 
air,  however,  may  be  taken  from  the  outside  for  the  pur- 
pose of  ventilation,  thus  requiring  the  same  amount  of  air 


HEATING  AND  VENTILATION 


to    be   exhausted   at  the   room  temperature    and   causing  an 
increased  cost  of   operation,  as  discussed  in  Art.    36. 

33.  Essentials  of  the  Furnace  System: — Fundamentally, 
this  installation  must  contain:  first,  a  furnace  upon  proper 
settings;  second,  a  carefully  designed  and  constructed  sys- 
tem of  fresh  air  supply  and  return  ducts;  and  third,  the 
warm  air  distributing  leaders,  stacks  and  registers.  Fig. 
12  shows,  in  elevation,  a  common  arrangement  of  these 
essentials,  and  gives,  also,  the  air  circulation  by  arrovv 


directions.  The  installation  shown  is  rendered  flexible  In 
operation  by  the  basement  dampers,  proper  adjustment  of 
which  will  allow  fresh  air  to  be  taken  from  either  side 


FURNACE    HEATING  47 

of  the  house  or  furnished  to  the  pit  under  the  furnace  by  the 
duct  from  the  first  floor  rooms.  This  return  register  is 
usually  placed  in  the  hall,  under  the  stairway,  or  in  some 
room  which  is  generally  in  open  connection  with  the  other 
rooms  on  the  first  floor,  as  a  large  living  room. 

34.  Points  to  foe   Calculated  in  a  Furnace  Design: — Be- 
sides   the    calculated    heat   loss,    H,    which    of   course    would 
probably    be    the    same    for    all    methods    of    heating,    other 
points   in  furnace  design  would  be  taken  up  in  the  follow- 
ing   order:    first,    find    the    cubic    feet    of    air    needed    as    a 
heat  carrier  and  determine  if  this  amount  of  air  is  sufficient 
for  ventilation;   then   calculate   the   areas   of  the   following: 
net    heat    register,    gross    heat    register,    heat     stack,     net 
vent  register,  gross  vent  register,  vent  stack,  leader  pipes, 
fresh  air  duct  and  total  grate  area.     From  the  total  grate 
area  the  furnace  may  be   selected. 

35.  Air  Circulation  in  Furnace  Heating: — The  use  of  air 

in  furnace  heating  may  be  considered  from  two  standpoints, 
each  very  distinct  in  itself.  First,  air  as  a  Tieat  carrier; 
second,  air  as  a  Health  preserver.  The  first  may  or  may  not 
provide  fresh  air;  it  merely  provides  enough  air  to  carry 
the  required  amount  of  heat  from  the  furnace  to  the  rooms, 
i.  e.,  to  take  the  place  of  the  heat  lost  by  radiation  plus 
the  small  amount  that  is  carried  away  by  the  natural  in- 
terchange of  air  from  within  to  without  the  building,  as 
would  be  true  in  any  residence  that  is  not  especially  planned 
to  provide  ventilation.  With  certain  allowable  temperatures 
at  the  various  parts  of  the  system,  this  volume  of  air  may 
be  easily  calculated.  One'  point  here  should  be  remembered: 
when  the  cubic  feet  of  air  per  hour  as  a  heat  carrier  is 
found  at  the  register,  this  volume  remains  the  same,  no 
matter  if  it  enters  the  furnace  through  a  duct  from  within 
or  without  the  building.  So  this  plan  may  be  both  a  heat 
carrier  and  a  ventilator  if  desired,  subject  only  to  the 
amount  of  air  required.  The  second  plan  requires  that 
enough  air  be  sent  to  the  rooms  to  provide  ventilation.  If 
this  amount  is  less  than  that  needed  as  a  heat  carrier,  all 
well  and  good,  the  first  amount  will  be  used;  but  if  it 
should  be  greater,  then  the  first  amount  will  need  to  be 
increased  arbitrarily  to  agree.  This  increased  volume  will 
then  be  used  instead  of  that  calculated  as  a  heat  carrier 


48  HEATING  AND  VENTILATION 

only.  As  previously  stated,  the  cubic  feet  of  air  per  hour 
as  a  ventilator  may  be  taken  as  1800  N,  where  N  is  the 
number  of  persons  to  be  provided  for.  See  Art.  9. 

36.  Air  Required  per  Hour  as  a  Heat  Carrier: — A  safe 
temperature  t,  of  the  circulating  air  as  it  leaves  the  heat 
register,  is  130  degrees.  This  may  at  times  reach  140  de- 
grees but  it  is  not  well  to  use  the  higher  value  In  the 
calculations.  If,  as  is  nearly  always  the  case,  the  room 
air  temperature,  f,  is  70  degrees,  the  incoming  air  will 
drop  in  temperature  through  60  degrees  and,  sin'ce  one  cubic 
foot  of  air  can  be  heated  through  55  degrees  by  one  B.  t.  u. 
(see  Art.  27.),  it  will  give  off  60  -H  55  =  1.09  (say  1.1)  B.  t.  u. 

Let  Q  =  cubic  feet  of  air  per  hour  as  a  heat  carrier;  H 
=  total  heat  loss  in  B.  t.  u.  per  hour  by  formula;  t  =  tern- 
perature  of  the  air  at  the  register;  and  V  —  temperature  of 
the  room  air;  then 

55  H 
Q  =  •  (14) 

t  —  r 

which   for  ordinary  furnace  work  becomes 

H 

Q  = 

1.1 

Now  if  this  air  is  not  allowed  to  escape  from  the  building, 
Fig.  12,  but  is  taken  back  to  the  furnace  and  recirculated, 
the  only  loss  of  heat  will  be  H,  that  calculated  by  the 
formula;  but  as  a  matter  of  fact,  air  thus  used  would  soon 
become  contaminated  and  wholly  unfit  for  the  occupants  to 
breathe,  hence,  it  is  customary  to  exhaust  through  ventil- 
ating flues,  either  a  part  or  all  of  the  air  sent  from  the 
furnace.  This  makes  an  additional  loss  of  heat  from 
the  building  corresponding  to  the  drop  In  degrees  from  70 
to  that  of  the  outside  air.  Let  the  temperature  of  the  out- 
side air,  to,  be  0  degrees,  then  the  resulting  heat  loss  would 
be  (see  also  Art.  102  on  blower  work.)  H'  =  H  plus  (t'  —  to) 
divided  by  55  and  multiplied  by  the  amount  of  air  intro- 
duced for  ventilation.  Stated  as  a  formula  for  the  special 
conditions,  this  becomes 

H'  =   H   -f    1.27   Qr  (15) 


FURNACE    HEATING  49 

Take  for  illustration  the  Sitting  Room,  Fig.  14,  and 
consider  it  under  three  conditions  on  a  zero  day:  first,  when 
all  the  air  is  recirculated;  second,  when  only  enough  air  is 
exhausted  to  give  good  fresh  air  for  ventilation;  third, 
when  all  the  air  is  exhausted.  Under  the  first  case  the  loss 
H,  by  formula  is,  say,  14000  B.  t.  u.  per  hour  and  no  other 
loss  is  experienced.  In  the  second  case,  let  three  people  oc- 
cupy the  room  and  allow  1800  cubic  feet  of  fresh  air  per  hour 
for  each  person,  or  a  total  of  5400  cubic  feet  per  hour,  then 
the  total  heat  loss  from  the  room  will  be,  Formula  13, 
14000  +  5400  X  70  -r-  55  =  20873,  say  21000  B.  t.  u.  The 
third  case,  where  all  the  air  is  exhausted,  gives  14000  -4-  1.1 
=  12727  cubic  feet  of  fresh  air  exhausted  at  70  degrees, 
which  requires  the  same  amount  of  fresh  air  being  raised 
from  zero  to  70  degrees  to  replace  it.  This  necessitates  the 
application  of  12727  X  70  +  55  =  16198  B.  t.  u.  additional, 
or  a  total  heat  loss  of  30198,  say  30000  B.  t.  u.  per  hour. 

The  second  condition  is  that  which  would  be  found  most 
satisfactory.  It  is  evident  from  inspection  that  the  cubic 
feet  of  air  necessary  as  a  heat  carrier  will  supply  excessive 
air  for  ventilation  in  the  average  residence,  and  the  de- 
signer need  not  necessarily  consider  the  amount  of  air  for 
ventilation  except  as  he  wishes  to  investigate  the  size  of 
the  furnace,  the  amount  of  coal  burned  or  the  cost  of 
heating;  the  latter  being  in  direct  proportion  to  the  respect- 
ive total  heat  losses. 

APPLICATION. — Referring  to  Table  IX,  page  56,  the  calcu- 
lated amount  of  air  per  hour  for  the  various  rooms  and  for 
the  entire  building  may  be  found. 

37.  Is  this  Amount  of  Air  Sufficient  for  Ventilation  if 
Taken  from  tae  Outside? — Take  the  13  X  15  X  10  foot  sitting 
room,  Fig.  14.  Let  the  estimated  heat  loss  be  14000  B.  t.  u. 
per  hour,  then  Q  =  12727  cubic  feet.  With  a  room  volume 
of  1950  cubic  feet,  the  air  will  change  6.5  times  per  hour, 
and,  allowing  1800  cubic  feet  of  air  per  person,  will  supply 
seven  people  with  good  ventilation  if  fresh  air  be  used. 
Stated  as  a  formula,  this  would  be 

3  H 

y  = =: approx.  (16) 

1.1  X  1800  2000 

As  a  matter  of  fact,  ventilation  for  half  this  number  would 

be  ample  in  an  ordinary  residence  room  excepting  on  extraor- 


50  HEATING  AND  VENTILATION 

dinary  occasions.  So  it  would  seem  that  the  subject  of 
ventilating  air  will  be  more  than  taken  care  of  if  the  ducts 
and  registers  are  planned  to  carry  air  for  heating  purposes 
only. 

38.  Given  the  Heat  Loss  //  and  the  Volume  of  Air  Qr  for 
any  Room,  to  find  /,  the  Temperature  of  the  Air  Entering:  at 
the  Register: — If  for  any  reason  Q  Is  not  sufficient  for  ven- 
tilation, then  more  air  must  be  sent  to  the  room  and  the 
temperature  dropped  correspondingly  to  avoid  overheating 
the  room.  Let  Qf  =  total  volume  of  air  per  hour,  including 
extra  air  for  ventilation,  measured  at  the  register,  then 

55  H 

t  =  70  H (17) 

Q' 

APPLICATION. — Suppose  it  were  necessary  to  send  18000 
cubic  feet  of  fresh  air  to  this  sitting  room  per  hour  to  ac- 
commodate ten  people,  the  temperature  of  the  air  at  the 
register  should  be 

55  X  14000 

t  =s  70  +  =  113°. 

18000 

30.  Net  Heat  Registers:— The  \elocity  of  the  air  v, 
as  it  leaves  the  heat  register,  varies  from  3  to  4  feet  per 
second  according  to  different  designers.  The  first  figure 
is  objected  to  by  some  because  it  gives  too  large  register 
areas;  while  the  latter  value  is  claimed  to  be  great  enough 
that  the  occupants  of  the  room  will  notice  the  movement 
of  the  air.  Practice  no  doubt  tends  to  the  higher  velocity. 
Most  heat  registers  in  residences  are  placed  at  the  floor 
line.  If,  however,  they  be  placed  above  the  heads  of  the 
occupants  of  the  room  (see  Art.  94),  higher  velocities  than 
the  ones  named  can  be  used.  The  general  formula  for  net 
registers  is 

IT  X  55  X  144 

N.  H.  R.  =  .  (18) 

(f —  f )  x  v  X  3600 

Assuming  a  mean  velocity  of  3.5  feet  per  second,  and 
60  degrees  drop  in  temperature  from  the  register  to  the 
room,  then  the  square  inches  of  net  register  for  any  room 
are  found  by  the  formula: 

H  X  55  X  144 

y.  B.  R.  = =  .01  H  (19) 

60  X  3.5  X  3600 


FURNACE    HEATING  51 

40.  Net  Vent  Registers: — Vent  registers   should   be   put 
in  with  any  furnace  plant,  although  this  is  not  always  done. 
In  order  that  any  room  may  be  heated  properly,  it  is  abso- 
lutely necessary  that  the   cold  air  in  the  room   be  allowed 
to  escape  to  give  room  for  the  heated  air  to  come  in.     This 
in  some  cases  is  done   by   venting  through   doors,  windows 
or    transoms.      A    tightly    closed    room    cannot    be    properly 
heated   by   a   furnace. 

If  all  the  air  were  to  pass  out  the  vent  register  at  the 
same  velocity  as  it  entered  through  the  heat  register,  the 
area  of  the  vent  register  would  be  to  the  area  of  the  heat 
register  as  the  ratio  of  the  absolute  temperatures  of  the 
leaving  and  entering  air;  that  is,  the  area  of  the  vent 
register  =  .9  of  the  area  of  the  heat  register.  As  a  matter 
of  fact  since  some  of  the  air  leaves  the  room  through  other 
openings,  the  vent  register  need  not  be  so  large.  Practice 
has  decided  this  area  to  be  about 

N.  V.  R.  —  .008  H  =  .8  N.  H.  R.  (20) 

41.  Gross  Register  Area: — The  nominal  size,  or  catalog 
size,  of  the  register  is  usually  stated  as  the  two  dimensions 
of   the   rectangular   opening   into    which    it    fits,    and    varies 
from  1.5  to  2  times  the  net  area.     The  larger  value  is  prob- 
ably the  'safer  to  follow   unless   the  exact  value  be  known 
for  any  special  make  of  register. 

G.  R.  =  (1.5  to  2)  times  the  net  register  (21) 

Round  registers  may  be  had  if  desired.     Register  sizes  may 
be  found  in  Tables  14  and  17,  Appendix. 

42.  Heat  Stacks: — To  get  the  proper  sizes  of  the  stacks 
in  any  heating  system  is  a  very  important  part  of  the  de- 
sign of  that  system.     By  some  designers  the  cross  sectional 
area  is  taken  roughly  as  a  certain  ratio  to  that  of  the  net 
register.      This    has    been    quoted    anywhere   from    50    to    90 
per   cent.      Such    wide    variations    between    extremes    of   air 
velocity  should  certainly  require  careful  application.     Prof. 
Carpenter   in  H.   and  V.   B.   Arts.    54   and   141,    suggests    4,   5 
and  6  feet  per  second  respectively,  as  the  air  velocities  for 
the    first,    second   and    third   floors.      Mr.    J.    P.    Bird,    in    the 
"Metal  Worker"  of  Dec.  16,   1905,  uses  280,  400  and  500  feet 
per  minute,  which  is  approximately  4.5,   6.5  and  8  feet  per 
second   under  like   conditions.      The   formula   for   cross    sec- 


52  HEATING  AND  VENTILATION 

tional  area  of  the  heat  stack,  from  formula  19,  then  becomes, 
if  the  velocities  are  4,  5.5  and  7  feet  per  second, 

S  X  55  X  144  f. 0091  Hist   floor") 

H.   S.  =  =   \  .00665  2nd  floor  !-    (22) 

60  X  (4,  5.5  or  7)   X  3600          [.005253rd  floorj 

The  air  velocity  in  the  stack  is  based  upon  the  formula 
v  =  \/2gh,  where  h  =  (effective  height  of  stack)  X  (t  —  t')  -~ 
(460  +  *');  v  is  in  feet  per  second;  *  is  the  temperature  of 
the  stack  air  and  ?  is  the  temperature  of  the  room  air. 
The  calculated  results  from  this  formula  are  much  higher 
than  those  obtained  in  practice  because  of  the  shape  of 
cross  sections  of  the  stack,  the  friction  of  its  .sides  and  the 
abrupt  turns  in  it. 

From  the  basis  of  the  net  register  (figured  at  3.5  feet 
per  second)  the  two  quotations  by  Carpenter  and  Bird  give 
heat  stack  areas  as  follows:  first  floor,  80  to  88  per 
cent.;  second  floor,  55  to  70  per  cent.;  and  third  floor,  44  to 
60  per  cent.  Good  sized  stacks  are  always  advisable  (see 
Art.  55),  but  because  of  the  limited  space  between  the  stud- 
ding it  becomes  necessary  at  times  to  put  in  a  stack  that 
is  too  small  or  to  increase  the  thickness  of  the  wall,  a  thing 
which  the  architect  is  occasionally  unwilling  to  do.  From 
the  above  figures,  checked  by  existing  plants  that  are 
working  satisfactorily,  the  following  approximate  figures, 
reduced  to  the  basis  of  the  net  heat  register  area,  will  no 
doubt  give  good  results. 

{.8     times  the  net  heat  register.  1st    floor"! 
.66  times  the  net  heat  register.  2nd  floorj      (23) 
.5     times  the  net  heat  register.  3rd  floorj 

43.  Vent  Stacks:— V.  S.  =  . 8  H.  S.  (24) 

44.  Leader  Pipes: — Since  all  the  air  that  passes  through 
the    stacks    must   pass   through    the    leader   pipes,    it   seems 
reasonable  to  assume  that  the  areas  of  the  two  would  be 
equal.     It   must  be  remembered,    however,   that   the   stacks, 
because    of  their    vertical   position,    offer    less    resistance    in 
friction,    while    on  the   other   hand    the   leader    pipes,    being 
nearly    horizontal    and    having    more    crooks    and    turns    in 
them,  will  have  considerable  friction  and  will  consequently 
retard  the  air  to  a  greater  degree.     There  will  also  be  some 
loss    of   temperature   in    the    air    as    it    passes    through    the 
leader  pipes,    consequently   the   volume   of   air   entering  the 
leader   from   the    furnace   will    be   greater   than   that    going 
up  the  stack. 


FURNACE   HEATING  53 

It  would  be  well,  from  the  above  reasons,  to  make  the 
area  of  the  leader  pipes 

L.  P.  =  (1.1  to  1.2)  times  the  stack  area,  (25) 

the  exact  figures  to  depend  upon  the  length  and  inclination 
of  the  leader  and  the  selection  of  the  diameter  of  the  pipe. 

45.  Fresh  Air  Duct: — The  area  of  the  fresh  air  duct  is 
determined  largely  by  experience  as  in  the  case  of  the  vent 
register.     It  is  generally  taken 

F.  A.  D.  =  .8  times  the  total  area  of  the  leaders.        (26) 

Assume  the  average  velocity  of  the  air  in  the  leaders  to  be 
6  feet  per  second  and  the  area  of  the  fresh  air  duct  to  be 
as  shown  above,  then,  if  the  air  in  each  were  of  the  same 
temperature,  the  velocity  in  the  fresh  air  duct  would  be 

6  -~    .  8  =   7.5   feet  per   second;    but   since  the  temperatures 
are  different  the  velocities  will  be  in  proportion  to  the  ab- 
solute temperatures.     Hence  it  is,  at  0  degrees,  .78  X  7.5  — 
5.8;  at  25  degrees,    .82  X  7.5  =  6.2;  and  at  50  degrees,    .88 
X    7.5   =   6.6   feet   per   second.      It   is   seen   by   this,   that   al- 
though the  area   of  the   fresh   air   duct  is  contracted   to   80 
per    cent,    of    that    of    the    leaders,    the    velocity    is    in    all 
cases  below  that  of  the  leaders.     It  is  always  well   to  have 
a  fresh   air   duct  that  is   large   in   cross   sectional   area   and 
free  from  obstructions  and  sharp  turns. 

46.  Grate  Area: — The  grate   area  of  a  furnace   is  esti- 
mated from   the   total   heat   lost   from  the    building,   figured 
on  a  basis  of  a  certain  degree  of  ventilation.     In  obtaining 
the  grate  area  it  is  necessary  to  assume  the  quality  of  the 
coal,   the   efficiency   of   the   furnace   and   the  pounds   of   coal 
burned  per  hour  per  square   foot  of  grate.     The  quality  of 
coal  selected  would  be  between  12000  and  14000  B.  t.  u.  per 
pound   as   shown   in  Table    11,   Appendix.     The    efficiency   of 
the   average   furnace    is   about    60   per   cent.;    and  the      coal 
burned  per  square  foot  of  grate  per  hour  ranges  from  3  to 

7  pounds.     Concerning  the  last  point  there  may  be  a  wide 
difference  of  opinion.     Higher  temperatures  in  the  combus- 
tion  chamber   are    conducive   to    economy;    hence,    to    reduce 
the  size  of  the  fire  pot  and  fire  small  amount  of  coal  with 
greater    frequency    would    seem    to    be   ,the    ideal    way.      On 
the   other  hand,   with   high  temperatures  in  the  combustion 
chamber,    the   loss   up   the   chimney   is    increased.     Probably 


54  HEATING  AND  VENTILATION 

the  one  factor  which  Is  most  effective  in  settling  this  point 
is  the  inconvenience  of  frequent  firing.  Furnaces  are 
charged  from  two  to  four  times  each  twenty-four  hours. 
This  requires  a  good  sized  fire  pot  and  a  possibility  of 
banking  the  fires.  To  allow  5  pounds  per  hour  is  probably 
as  good  an  average  as  can  be  made  for  most  coals  in  fur- 
nace work. 

Let  H'  =  total  heat  loss  from  the  building  including: 
ventilation  loss;  E  =  efficiency  of  the  furnace;  f  =  value  of 
coal  in  B.  t.  u.  per  pound;  and  p  =  pounds  of  ctfal  burned 
per  square  foot  of  grate  per  hour;  then  the  formula  for  the 
square  inches  of  grate  area  is 

H'  X  144 

O.  A.  =  (27) 

E  X  /  X  p 

APPLICATION. — In  the  typical  illustration,  the  total  heat  loss 
on  a  zero  day  by  formula  is,  say,  100000  B.  t.  u.  per  hour. 
This  will  require  90909  cubic  feet  of  air  as  a  heat  carrier. 
Assuming  as  a  maximum  that  10  people  will  be  in  the 
house  and  that  they  will  need  18000  cubic  feet  of  fresh  air 
per  hour  for  ventilation,  this  air  will  carry  away  approx- 
imately 22900  B.  t.  u.  per  hour,  making  a  total  heat  loss 
from  the  building  of  122900  B.  t.  u.  per  hour.  Now,  if  the 
furnace  is  60  per  cent,  efficient  and  burns  5  pounds  of 
14000  B.  t.  u.  coal  per  hour  per  square  foot  of  grate,  we 
will  have 

122900  X  144 

0.  A.  = =  421  square  inches  —  23.2  inches 

.60  X  14000  X  5 

diameter.  With  coal  at  13000  B.  t.  u.  per  pound,  the  grate 
would  be  454  square  inches  or  24  inches  diameter.  In  either 
case  a  24  inch  grate  would  be  selected.  With  the  assump- 
tions as  made  above,  the  formula  becomes  G.  A.  =  .0035  H' 
for  the  better  grade  of  coal,  and  G.  A.  =  .0037  Hf  for  the 
poorer  grade,  from  which  the  following  approximate  form- 
ula may  be  taken: 

O.  A.  square  inches  =  .0036  H'  (28) 

47.     Heating   Surface: — The   amount  of  heating   surface  *•- 
to  be  required  in  any  furnace  is  rather  an  indefinite  quantity.    -1 
Manufacturers   differ  upon  this  point.     Some   standard  may 
soon  be  looked  for  but  at  present  only  rough  approximations 
can  be  stated.     One  of  the  chief  difficulties  is  in  determin- 
ing what  is,  or  what  is  not,  heating  surface.     Some  quota- 


FURNACE  HEATING  55 

tions  no  doubt  include  some  surface  in  the  furnace  that  is 
very  inefficient.  In  estimating1,  only  prime  heating  surface 
should  be  considered,  i.  e.,  such  plates  or  materials  having 
direct  contact  with  the  heated  flue  gases  on  one  side  and 
the  warm  air  current  on  the  other.  If  these  plates  trans- 
mit K,  B.  t.  u.  per  square  foot  per  degree  difference  of  tem- 
perature, tz,  per  hour;  if,  also,  one  square  foot  of  grate 
gives  to  the  building  E  X  /  X  p  B.  t.  u.  per  hour,  there  will 
be  the  following  ratio  between  the  heating  surface  and 
grate  surface: 

B.  8.  E  f  p 

=  (29) 

G.  S.  Kt, 

APPLICATION. — Let  the  value  K  tz  be  2500,  as  suggested  by 
W.    G.    Snow,   Trans.   A.   S.   H.   &  V.   E.,    1906,   page   133,   and 
with  the  same  notations  as  in  Art.  46  obtain 
H.  8.  .6  X  14000  X  5 


G.  8.  2500 


=  17 


In  practice  this  ratio  varies  anywhere  between  12  and  30. 

48.  Application  of  the  Above  Formula**  to  a  Ten  Room 
Residence: — In  every  design  the  calculations  should  be  made 
very  complete  and  the  results  tabulated  for  easy  reference 
and  as  a  means  of  comparison.  Such  a  tabulation  is  shown 
in  Table  IX,  giving  all  the  calculated  quantities  necessary  in 
the  installation  of  the  furnace  system  illustrated  in  Figs. 
13,  14  and  15.  The  value  of  so  condensing  the  work  will  be 
readily  apparent.  The  tabulation  of  the  values  used 
for  the  various  terms  of  the  formula  facilitates  checking 
and  the  detection  of  errors.  Plans  should  be  carefully 
drawn  to  scale  and  accompanied  by  a  sectional  elevation. 
The  scale  should  be  as  large  as  can  conveniently  be  made. 
The  location  of  the  building  with  reference  to  the  points 
of  the  compass  should  always  be  given,  as  well  as  the 
heights  of  ceilings  and  the  principal  dimensions  of  each 
room.  There  will  be  a  wide  variety  of  practice  in  making 
allowance  for  exposure,  floors,  ceilings,  closets  and  small 
rooms  not  considered  of  sufficient  importance  to  have  inde- 
pendent heat.  The  personal  element  enters  into  this  part  of 
the  work  very  largely.  Such  points  as  these  are  left  to 
the  discretion  of  the  designer  who,  after  having  had  con- 
siderable experience  is  able  to  judge  each  case  very  closely. 


56 


HEATING  AND  VENTILATION 


TABLE    IX. 
Formula.  H  =  «?  +   .25  W  +   .02  ntf)    70 


H  O 

4» 

55 

Dining 
Boom 

1 
OQ 

Kitchen 

a 

JH 

jq 

D 

Chamber 

2 

Chamber  i 

h 
O 

I 

03 

1 

O 

38 
85 
78 
2 
14000 
12727 
140 
14x16 

28 
28 
84 
2 
10800 
9818 
108 
12x14 

42 
52 
78 
2 
18250 
12045 
182 
14x16 

28 
65 
56 
2 
11900 
10818 
119 
12x14 

29 
78 

104 
3 

14000 

42 
45 
85 
1 
9400 
8544 
94 
12x12 
61 
67 
75 
10x12 
45 

88 
60 
86 
1 
9850 
9854 
98 
12x12 
64 
70 
78 
10x12 
48 

26 
81  ' 
1 
6600 
6000 
66 
9x12 
43 
47 
53 
8x10 
32 

30 
22 
1 

5600 
5091 
56 
8x10 
36 
40 
45 
8x10 
27 

14 
17 
26 
2 
4400 
4000 
44 
8x10 
28 
81 
85 
8x8 
22 

315 
481 

99800 

.25  W 

H- 

Q 

12727 
140 
14x16 

Area  of  Net  Heat  Register 
Heat  Register  Size    

711 

Area  of  Heat  Stack  

Area  of  Leader  

100 
112 
12x14 
67 

77 
86 
10x12 
52 

94 
106 
12x14 
64 

85 
95 
12x12 
60 

100 
112 
12x14 
67 

Area  of  Net  Vent  Register 
Vent  Register  Size  

Area  of  Vent  Staok 

Remarks 

Allow  for  cold  floor 

low  10  per  cent,  for  closet 
and  exposure 

1 

H 

o> 

s 
i 

& 

o 
o 

low  15  per  cent,  for  pantry 
stair  and  exposure 

low  for  floor  and  hall  way 
on  second  floor 

low  10  per  ct.  for  exposure 

9 

1 

"o 

tn 

S-i 

i 

i 

10 

;-, 

O 

Is 
M 

o  o> 

Add  closet  to  room 

Allow  10  per  cent.for  closet 
and  exposure 

3 

5J 

3 

* 

* 

Diameter  of  grate  allowing  ventilation  for  ten  people  = 
24  inches.  Cold  air  duct  =  569  square  inches  =  18  X  32  inches. 

In  selecting  the  various  stacks  and  leaders  it  would  be 
well  to  standardize  as  much  as  possible  and  avoid  the  extra 
expense  of  installing  so  many  sizes.  This  can  be  done  if 
the  net  area  is  not  sacrificed. 


BURNACE  HEATING 


57 


Fig.   33. 


58 


HEATING  AND  VENTILATION 


FURNACE  HEATING 


59 


«5ctonD  FIPOR.  PLAN 


Fig.   15. 


CHAPTER  V. 

FURNACE  HEATING  AND  VENTILATING. 

SUGGESTIONS  ON  THE  SELECTION  AND  INSTALLATION  OF  FURNACE 
HEATING    PARTS. 

49.  Selection  of  the  Furnace: — In  selecting  a  furnace 
for  residence  use  or  other  heating  service,  special  attention 
should  be  paid  to  the  following-  points:  easy  movement  of 
the  air,  arrangement  and  amount  of  heating  surface,  shape 
and  size  of  the  fire  pot,  method  of  feeding  fuel  to  the  fire 
and  type  and  size  of  the  grate.  The  furnace  gases  and  the 
air  to  be  heated  should  not  be  allowed  to  pass  through  the 
furnace  in  too  large  a  unit  volume  or  at  too  high  a  velocity. 
The  gases  should  be  broken  up  in  relatively  small  volumes, 
thus  giving  an  opportunity  for  a  large  heating  surface. 
Concerning  the  gas  passages  themselves,  it  may  be  said 
that  a  number  of  small,  thin  passages  will  be  found  more 
efficient  than  one  large  passage  of  equal  total  area.  This 
is  plainly  shown  in  a  similar  case  by  comparing  the  effi- 
ciency of  the  water-tube  or  tubular  boiler  with  that  of 
the  old  fashioned  flue  boiler;  i.  e.,  a  large  heating  surface 
is  of  prime  importance.  Again,  it  is  desirable  that  the 
total  flue  area  within  the  furnace  should  be  great  enough 
to  allow  the  passage  of  large  volumes  of  air  at  low  velocities, 
rather  than  small  volumes  at  high  velocities.  This  permits 
of  less  forcing  of  the  fire  and  consequently  lowers  the  tem- 
perature of  the  heating  surface.  The  latter  point  will  be 
found  valuable  when  it  is  remembered  that  metal  at  high 
temperatures  transmits  through  its  body  a  greater  amount 
of  impure  gases  from  the  coal  than  when  at  low  tempera- 
tures. Concerning  velocities,  it  may  be  said  that  on  account 
of  the  low  rate  of  transmission  of  heat  to  or  from  the 
gases,  long  flue  passages  are  necessary,  so  that  gases  mov- 
ing at  a  normal  rate  will  have  time  to  give  off  or  to  take 
up  a  maximum  amount  of  heat  before  leaving  the  furnace. 

Air  is  heated  chiefly  by  actual  contact  with  heated  sur- 
faces and  not  much  by  radiation.  Consequently,  the  ef- 
ficiency of  a  furnace  is  increased  when  it  is  designed  so 
that  the  gases  a>nd  air  in  .their  movement  impinge  perpen- 
dicularly upon  the  heated  surfaces  at  certain  places.  This 


FURNACE  HEATING 


61 


point  should  not  be  so  exaggerated  that  there  would  be 
serious  interference  with  the  draft.  The  efficiency  is  also 
increased  if  the  general  movement  of  the  two  currents  be 
in  opposite  directions. 

Furnaces  for  residences  are  usually  of  the  portable  type, 
Fig.  16,  the  same  being  enclosed  in  an  outer  shell  composed 
of  two  metal  casings  having  a  dead  air  space  or  an  asbes- 
tos insulation  between  them.  Some  of  the  larger  sized 


Fig.   16. 

plants,  however,  have  the  furnace  enclosed  in  a  permanent 
casement  of  brick  work,  as  in  Fig.  17.  Each  of  the  two 
types  of  furnaces  give  good  results.  The  points  usually 
governing  the  selection  between  portable  and  permanent 
settings  are  price  and  available  floor  space. 

The  cylindrical  fire  pot  is  probably  better  than  a  con- 
ical or  spherical  one,  there  being  less  danger  of  the  fire 
clogging  and  becoming  dirty.  A  lined  fire  pot  is  better 
than  an  unlined  one,  because  a  hotter  fire  can  be  maintained 
in  it  with  less  detriment  to  the  furnace.  There  is  of  course 
a  loss  of  heating  surface  in  the  lined  pot,  and  in  some  forms 
of  furnaces  the  fire  pot  is  unlined  to  obtain  this  increased 


62 


HEATING  AND  VENTILATION 


heating  surface.  It  seems  reasonable  to  assume,  however, 
that  the  lined  pot  is  longer  lived  and  contaminates  the  air 
supply  less. 


Pig.   17. 


Fig.   18. 


FURNACE  HEATING 


63 


Some  form  of  shaking  or  dumping  grate  should  be  se- 
lected, as  a  stationary  grate  is  far  from  satisfactory.  Care 
should  be  exercised  also  in  the  selection  of  the  movable 
grate,  as  some  forms  not  only  stir  up  the  fire  but  permit 
much  of  it  to  fall  through  to  waste  when  being  operated. 

The  fuel  is  fed  to  the  fire  pot  from  the  door  above  the 
fire.  This  is  called  a  top-feed  furnace.  In  some  forms,  how- 
ever, the  fuel  is  fed  up  through  the  grate.  This  is  called 
the  under-feed  furnace,  Fig.  18,  and  is  rapidly  gaining  in 
favor.  The  latter  type  requires  a  rotary  ring  grate  with 
the  fuel  entering  up  through  its  center. 

The  size  of  the  furnace  may  be  obtained  from  the  estimated 
heating  capacity  in  cubic  feet  of  room  space  as  given  in  the 
sample  Table  16,  Appendix.  Another  and  perhaps  a  bet- 
ter way,  and  one  that  serves  as  a  good  check  on  the  above, 
is  to  select  a  furnace  from  the  calculated  grate  area.  See  Art. 
46.  Having  selected  the  furnace  by  the  grate  area,  check 
this  with  the  table  for  the  estimated  heating  capacity 
and  the  heating  surface  to  see  if  they  agree. 

What  is  known  as  a  combination  heater  is  shown  in 
Fig.  19.  It  is  used  for  heating  part  of  the  rooms  of  a  resi- 
dence by  warm  air,  as  in 
regular  furnace  work,  and 
the  remainder  of  the  rooms 
by  hot  water.  In  this 
manner,  rooms  to  be  ven- 
tilated as  well  as  heated 
may  be  connected  by  the 
proper  stacks  and  leaders 
to  the  warm  air  deliveries 
of  such  a  combination 
heater,  while  rooms  requir- 
ing less  ventilation  or  heat 
only  may  have  radiators 
installed  and  connected  to 
the  flow  and  return  pipes 
shown  In  the  figure.  Also, 
because  of  the  difficulty 
in  heating  certain  exposed 
rooms,  with  warm/ air,  these 
rooms  may  be  supplied  by 
the  positive  heat  of  the 


Fig.  19. 
more  reliable  water  circulation. 


64  HEATING  AND  VENTILATION 

50.  Location  of  the   Furnace: — Where   other  things   do 
not   interfere,   a   furnace    should   be   set   as   near   the   center 
of  the  house   plan  as   possible.     Where  this   is   not  wise   or 
possible,  preference  should  be  given  to  the  colder  sides,  say 
the  north  or  west.     In  any  case,  it  is  advisable  to  have  the 
leader  pipes  as  near  the   same  length  as  can  be  made.  The 
lengtn    of   the   smoke   pipe   should   be   as   short   as   possible, 
but  it  will  be  better  to  have  a  moderately  long  smoke  pipe 
and  obtain  a   more  uniform  length  of  leader  pipes  than  to 
have   a    short   smoke    pipe    and    leaders    of    widely   different 
lengths. 

The  furnace  should  be  set  low  enough  to  get  a  good 
upward  slope  to  the  leaders  from  the  furnace  to  their  re- 
spective stacks.  This  should  be  not  less  than  one  inch  per  foot 
of  length  and  more  if  possible.  These  leader  pipes  should  be 
dampered  near  the  furnace. 

The  location  of  the  furnace  will  call  forth  the  best 
judgement  of  the  designer,  since  the  right  or  wrong  decis- 
ion here  can  make  or  mar  the  whole  system  more  com- 
pletely than  in  any  other  manner. 

51.  Foundation: — All    furnaces    should   have    directions 
from  the  manufacturer  to  govern  the  setting.     Each  type  of 
furnace    requires    a    special    setting    and    the    maker   should 
be°-t  be  able  to  supply  this   desired  Information   concerning 
it.     Such  information  may  be  safely  followed.     In  any  case 
the  furnace  should  be  mounted  on  a  level  brick  or  concrete 
foundation  specially  prepared  and  well  finished  with  cement 
mortar  on  the  inside,  since  this  interior   is  in  contact  with 
the  fresh  air  supply. 

52.  Fresh  Air  Duct: — This  is   best  constructed   of  hard 
burned   brick,    vitrified    tile    or    concrete,    laid    in   four    inch 
walls    with    cement    mortar    and    plastered    inside    with    ce- 
ment plaster,  all  to  be  air  tight.     The  top  should  be  covered 
with    flag    stones    with    tight    joints.      The    riser   from   this, 
leading  to  the  outside  of  the  building,  may  be  of  wood,  tile 
or   galvanized    iron,    and   the   fresh   air   entrance    should   be 
vertically  screened.     The  whole  should  be  with  tight  joints 
and  be  so  constructed  as  to  be  free  from  surface   drainage, 
dirt,    rats    and   other   vermin.      This    duct   may   be    made    of 
metal  or  boards  as  substitutes  for  the  brick,  tile  or  concrete. 
Board  construction  is  not  so  satisfactory,  although  it  is  the 


FURNACE  HEATING 


cheapest,  and  whenever  used  should  be  carefully  constructed, 
An  opening-  may  be  made  in  the  fresh  air  duct  near  the 
furnace  for  the  purpose  of  admitting  the  duct  which  carries 
the  recirculated  air  from  the  rooms  to  the  furnace.  Both 
of  these  ducts  should  have  dampers  that  may  be  opened  or 
closed.  See  Fig.  12.  Both  ducts  should  also  be  provided 
with  doors  that  can  be  opened  temporarily  to  the  cellar 
air.  Sometimes  it  is  desirable  to  have  two  or  more  fresh 
air  ducts  leading-  from  the  different  sides  of  the  house  to  the 
furnace  so  as  to  get  the  benefit  of 
any  change  in  air  pressure  on  the 
outside  of  the  building. 

Proper  arrangements  may  be 
made  for  pans  of  clear  water  in  the 
air  duct  near  the  furnace  to  give 
moisture  to  the  air  current,  although 
only  a  small  amount  of  moisture 
will  be  taken  up  at  this  point.  In 
most  cases  where  moistening  pans 
are  used,  they  are  installed  in  con- 
nection with  the  furnace  itself.  A 
good  way  to  moisten  the  air  fs  to 
have  moistening  pans  built  in  just 
behind  the  register  face,  Fig.  20. 
These  pans  are  shallow  and  should 
not  be  permitted  to  seriously  inter- 
fere with  the  amount  of  air  enter- 
ing- through  the  register. 


Fig.  20. 


53.  Recirculatlng  Duct: — A  duct  should  be  provided 
from  some  point  within  the  building,  through  the  cellar 
and  entering  into  the  bottom  of  the  furnace  or  into  the 
fresh  air  duct  near  the  furnace;  this  is  to  carry  the  warm 
air  from  the  room  back  to  the  furnace  to  be  reheated  for 
use  again  within  the  building.  In  many  cases  tin  or  gal- 
vanized iron  is  used  for  the  material  for  the  recirculating 
pipe.  Where  this  enters  the  furnace,  or  the  fresh  air  duct 
near  the  furnace,  it  should  be  planned  with  sufficient  turn 
so  that  the  air  would  be  projected  through  the  furnace,  thus 
placing  a  hindrance  to  the  fresh  cold  air  from  following 
back  through  this  pipe  to  the  rooms.  The  exact  location 
of  the  same  will  depend,  of  course,  on  the  location  of  the 
register  installed  for  this  purpose.  The  construction  of  the 


66 


HEATING  AND  VENTILATION 


duct  may  agree  with   the   similar  construction  of  the   fresh 
air    duct. 

54.  Leader  Pipes: — All  leader  pipes  should  be  round 
and  free  from  unnecessary  turns.  They  should  be  made 
from  heavy  galvanized  iron  or  tin  and  should  be  laid  to  an 
upward  pitch  of  not  less  than  one  inch  per  foot  of  length, 
and  more  if  it  can  possibly  be  given.  The  connections  with 
the  furnace  should  be  straight,  but  if  a  turn  is  necessary, 
provide  long  radius  elbows.  All  connections  to  risers  or 
stacks  should  be  made  through  long  radius  elbows.  Rect- 
angular shaped  loots  having  attached  collars  are  sometimes 
used,  but  these  are  not  so  satisfactory  because  of  the  im- 


Fig.   21. 


FURNACE  HEATING 


pirigemcnt  of  the  air  against  the  flat  side  of  the  stack;  also 
because  of  the  danger  of  the  leader  entering  too  far  into 
the  stack  and  thus  shutting  off  the  draft.  Leaders  should 
connect  to  the  first  floor  registers  by  long  radius  el- 
bows. Leader  pipes  should  have  as  few  joints  as  possible 
and  these  should  be  made  firm  and  air  tight.  Fig.  21  shows 
different  methods  of  connecting  between  leaders  and  stacks, 
also  between  leaders  and  registers. 

The  outside  of  all  leader  pipes  should  be  covered  to 
avoid  heat  loss  and  to  provide  additional  safety  to  the  plant. 
The  covering  is  usually  one  or  more  thicknesses  of  asbes- 
tos paper  or  mineral  wool. 

55.  Stacks  or  Risers: — The  vertical  air  pipes  leading  to 
the  registers  are  called  stacks  or  risers.  They  are  rect- 
angular or  oblong  in  section  and  are  usu- 
ally fitted  within  the  wall.  See  Big.  22. 
The  size  of  the  studding  and  the  distances 
they  are  set,  center  to  center,  limit  the 
effective  area  of  the  stack.  All  stacks 
should  be  insulated  to  protect  the  wood- 
work. This  is  done  by  making  the  stack 
small  enough  to  clear  the  woodwork  by 
at  least  one-quarter  inch  and  then  wrapping 
it  with  some  non-conducting  material 
such  as  asbestos  paper  held  in  place  by 
wire. 

Another  way,  and  one  which  is  prob- 
ably more  satisfactory,  is  to  have  pat- 
ented double  walled  stacks  having  an  air 
space  between  the  walls  all  around.  The 
outside  wall  is  usually  provided  with  vent 
holes  which  allow  the  circulation  of  air 
between  the  walls,  thus  protecting  any 
one  part  from  becoming  overheated.  All 
stacks  should  be  made  with  tight  joints 
and  should  have  ears  or  flaps  for  fasten- 
ing to  the  studding.  Patented  stacks  are 

made    in   standard   sizes   and   of  various   lengths.      The  sizes 
ordinarily   found   in    practice   are    about   as    given    in   Table 
17,   Appendix. 

A  stack    is   sometimes   run   up   in   a   corner   or   in   some 
recess   in   the   wall   of  a   room   where   its   appearance,   after 


Fig.   22. 


68  HEATING  AND  VENTILATION 

being  finished  in  color  to  compare  with  that  of  the  room, 
would  not  be  unsightly.  This  is  necessary  in  any  case 
where  the  stack  is  installed  after  the  building  is  finished. 
This  method  is  desired  by  some  because  of  its  additional 
safety  and  because  more  stack  area  may  be  obtained  than 
is  possible  when  placed  within  a  thin  wall. 

All  stacks  should  be  located  in  partition  walls  looking 
toward  the  outside  or  cold  side  of  the  room.  This  protects 
the  air  current  from  excessive  loss  of  heat,  as  would  be  the 
case  in  the  outside  walls.  It  also  provides  a  more  uniform 
distribution  of  air. 

The  area  of  the  stack  best  adapted  to  any  given  room 
is  another  point  in  furnace  work  which  brings  out  a  wide 
diversity  of  practice.  Results  from  different  installations 
show  variations  as  great  as  50  per  cent.  This  is  not  so 
noticeable  in  the  first  floor  rooms  as  it  is  in  those  of  the 
second  floor.  In  a  great  many  cases  the  architect  specifies 
light  partition  walls  between  large  upper  rooms,  say,  four 
inch  studding  set  sixteen  inch  centers,  between  twelve  foot 
by  fifteen  foot  rooms,  heavily  exposed.  From  theoretical 
calculation  of  heat  losses,  these  rooms  require  larger  stacks 
than  can  be  placed  between  studding  as  stated;  however,  it 
is  very  common  to  find  such  rooms  provided  for  in  this  way. 
One  possible  excuse  for  it  may  be  the  fact  that  the  room  is 
designed  for  a  chamber  and  not  for  a  living  room.  Any 
sacrifice  in  heating  capacity  in  any  room,  even  though  it  be 
used  as  a  sleeping  room  only,  should  be  done  at  the  sug- 
gestion of  the  purchaser  and  not  at  the  suggestion  of  the 
architect  or  engineer.  Every  room  should  be  provided  with 
facilities  for  heat  as  though  it  were  to  be  used  as  a  living 
room  in  the  coldest  weather,  then  there  would  be  fewer 
complaints  of  defective  heating  plants  and  less  migrating 
from  one  side  of  the  house  to  the  other  on  cold  days. 

This  lack  of  heating  capacity  for  any  room  is  some- 
times overcome  by  providing  two  stacks  and  registers  in- 
stead of  one.  This  plan  is  very  satisfactory  because  one 
of  the  registers  may  be  shut  off  in  moderate  weather.  How- 
ever, it  requires  an  additional  expense  which  is  scarcely 
justified.  A  possible  improvement  would  be  for  the  archi- 
tect to  anticipate  such  condition  and  provide  suitable 
partition  walls  so  that  ample  stack  area  could  be  put  in. 
The  ideal  conditions  will  be  reached  when  the  architect  act- 


FURNACE  HEATING 


ually  provides  air  shafts  of  sufficient  size  to  accommodate 
either  a  round  or  a  nearly  square  stack.  When  this  time 
comes  a  great  many  of  the  furnace  heating1  difficulties  will 
have  been  solved. 

A  double  stack  supplying  air  to  two  rooms  is  some- 
times used,  having  a  partition  separating  the  air  currents 
near  the  upper  end.  This  practice  is  questionable  because 
of  the  liability  of  the  pressure  of  air  in  the  room  on  the 
cold  side  of  the  house  forcing  the  heated  air  to  the  other 
room.  A  better  method  is  to  have  a  stack  for  each  room 
to  be  heated. 

56.  Vent  Stacks: — Vent  stacks  should  be  placed  on  the 
inner  or  partition  walls  and  should  lead  to  the  attic.     They 
may   there   be   gathered   together   in   one    duct   leading  to    a 
vent  through  the  roof  if  desired. 

57.  Air  Circulation  Within  the  Room: — The  location   of 
the   heat  register,   relative   to   the  vent  register,   will  deter- 


Fig.  23. 

mine  to  a  large  degree  the  circulation  of  the  air  within  the 
room.  Fig.  23,  a,  b,  c  and  d,  shows  clearly  the  effect  of  the 
different  locations.  The  best  plan,  from  the  standpoint  of 
heating,  is  to  enter  the  air  at  a  point  above  the  heads  of  the 


70  HEATING  AND  VENTILATION 

occupants  and  withdraw  it  from  the  floor  line,  at  or  near  the 
same  side  from  which  the  air  enters.  This  gives  a  more  uni- 
form distribution  as  shown  by  the  last  figure.  It  is  doubtful, 
however,  if  this  method  will  give  the  best  ventilation  in 
crowded  rooms  where  the  foul  air  naturally  collects  at  the 
top  of  the  room.  Furnace  heating  is  not  so  well  cared  for 
in  this  regard  as  are  the  other  forms  of  indirect  heating,  the 
air  being  admitted  at  the  floor  line  and  required  to  find  its 
own  way  out. 

58.  Fan — Furnace    Heating    System: — In    large    furnace 
installations  where  the  air  is  carried  in  long  ducts  that  are 
nearly,  if  not  quite,  horizontal,  and  where  a  continuous  sup- 
ply of  air  is  a  necessity  in  all  parts  of  the  building,  a  com- 
bination  fan   and   furnace   system   may   be    installed.      These 
are  frequently  found  in  hospitals,  schools  and  churches.     Such 
a    system   may   be   properly   designated   a   mechanical   warm 
air  system.     In  comparison  with   other  mechanical   systems, 
however,  it  is  simpler  and  cheaper.     The  arrangement  may 
be   illustrated  by  Fig.   66   with   the   tempering  coils   omitted 
and  the  furnace  substituted  for  the  heating  coils.     The  fan 
should  .always  be  between  the  air  inlet  and  the  furnace  so  as 
to  keep  a  slight  pressure  above  atmosphere  on  the  air.  side 
and   thus    reduce   the   leakage    of   the    fuel    gas   through   the 
joints    of    the    furnace.      By   this    arrangement    there    is    less 
volume  of  air  to  be  handled  by  the  fan  and  a  smaller  sized 
fan  may  be  used. 

Fan-furnace  systems  may  be  set  in  multiple  if  desired,  i. 
e.,  one  fan  "operating  in  connection  with  two  or  more  fur- 
naces. Paddle  wheel  fans  are  preferred,  although  the  disk 
wheel  may  be  used  where  the  pipes  are  large  and  where 
the  air  must  be  carried  but  short  distances.  For  fan  types 
see  Chapter  IX. 

59.  Suggestions  for  Operating  Furnaces: — Furnaces  are 
designated  hard  coal  and  soft  coal,  depending  upon  the  type  and 
the  construction  of  the  grate,  hence  the  grade   of  coal  best 
adapted  to  the  furnace  should  be  used.     The  size  of  the  open- 
ings in  the  grate  should  determine  the  size  of  the  coal  used. 

Keep  the  fire  pot  well  filled  with  coal  and  have  it  evenly 
distributed  over  the  grate. 

Keep  the  fire  clean.  Clinkers  should  be  removed  from 
the  fire  once  or  twice  daily.  It  is  not  necessary  to  stir  the 
fire  so  completely  as  to  waste  the  coal  through  the  grate. 


FURNACE  HEATING  71 

When  replenishing  a  poor  fire  do  not  shake  the  fire,  but 
put  some  coal  on  and  open  the  drafts.  After  the  coal  is  well 
ignited  then  clean  the  fire. 

The  ash  pit  should  be  frequently  cleaned,  because  an 
accumulation  of  ashes  below  the  grate  soon  warps  the  grate 
and  burns  it  out. 

Keep  all  the  dampers  set  and  properly  working. 

Have  a  damper  in  the  smoke  pipe  and  keep  it  open  only 
so  far  as  is  necessary  to  create  a  draft. 

Keep  the  water  pans  full  of  water. 

Clean  the  furnace  and  smoke  pipe  thoroughly  in  all  parts 
at  least  once  each  year. 

Keep  the  fresh  air  duct  free  from  rubbish  and  impurities. 

Allow  plenty  of  pure  fresh  air  to  enter  the  furnace  at  all 
times.  In  cold  weather  part  of  this  supply  may  be  cut  off. 

Have  the  basement  well  ventilated  by  means  of  outside 
wall  ventilators,  or  by  special  ducts  leading  to  the  attic. 
Never  permit  the  basement  air  to  be  circulated  to  the  living 
rooms. 

To  bank  the  fires  for  the  night,  clean  the  fire,  push  the 
coals  near  the  rear  of  the  grate,  cover  with  fresh  fuel  to 
the  necessary  depth  (this  will  be  found  by  experience),  set  the 
drafts  so  they  are  nearly  closed  and  partially  open  the  fire 
doors. 


72  HEATING  AND  VENTILATION 

REFERENCES. 
References  on  Furnace  Heating:. 

TECHNICAL  BOOKS. 

Snow,  Prin.  of  Heat,  p.  27.  Snow,  Furnace  Heat.,  p.  7.  I.  C  S., 
Prin.  of  Heat.  &  Vent.,  p.  1237.  Carpenter,  Heat.  &  Vent.  Bldgs.,  p. 
310.  Hubbard,  Power,  Heat.  &  Vent.,  p.  423. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Warm  Air  Furnace  Heating,  C.  L.  Hub- 
bard,  Nov.  1909,  p.  42;  Dec.  1909,  p.  45;  Jan.  1910,  p.  66;  Feb. 
1910,  p.  48;  March  1910,  p.  51;  May  1910,  p.  48;  Aug.  1910,  p. 
29.  Warm  Air  System  of  Heating  and  Ventilating,  R.  H. 
Bradley,  May  1910,  p.  32  Mechanical  Furnace  Heating  and 
Ventilating,  June  1910,  p.  49.  Heating  and  Vent.  System 
installed  in  Public  School,  Fairview,  N.  J.,  July  1910,  p.  47. 
Combined  System  of  Warm  Air  and  Hot  Water  Heat,  for  a 
Residence,  Jan.  1909,  p.  26.  Warm  Air  Heating  Installation 
in  a  Brooklyn  Residence,  March  1909,  p.  38.  The  Heating  and 
Ventilating  Magazine.  Advanced  Methods  of  Warm  Air  Heat- 
ing, A.  O.  Jones,  Aug.  1904,  p.  88.  Air  Pipes,  Sizes  Required 
for  Low  Velocities,  Oct.  1905,  p.  7.  Report  of  Committee 
(A.  S.  H.  V.  E.)  to  Collect  Data  on  Furnace  Heating,  Jan. 
1906,  p.  35.  An  Improved  Application  of  Hot  Air  Heating, 
A.  O.  Jones,  July  1906,  p.  31.  Domestic  Engineering.  Sanitation 
in  Hot  Air  Heating,  James  C.  Bayles,  Vol.  25,  No.  6,  Sept. 
25,  1903,  p.  261.  Trans.  A.  8.  H.  &  V.  E.  Test  of  Hot  Air  Grav- 
ity System,  R.  C.  Carpenter,  Vol.  IX,  p.  131.  Heat  Radiators 
using  Air  instead  of  Water  and  Steam,  Geo.  Alysworth,  Vol. 
IX,  p.  259.  Velocities  in  Pipes  and  Registers  in  a  Warm  Air 
System,  Vol.  XII,  p.  352.  Relative  Size  Hot  Air  Pipes,  Vol. 
XIII,  p.  270.  Velocity  of  Air  in  Ducts,  Vol.  VII,  p.  162. 


CHAPTER  VI. 

HOT  WATER  AND  STEAM  HEATING. 

DESCRIPTION  AND  CLASSIFICATION  OF  THE  SYSTEMS. 

60.  Hot   "Wafer   and   Steam    Systems    Compared   to    Fur- 
nace   Systems: — As    compared   to    the   warm    air   or    furnace 
plant,   the  hot  water  and  the   steam   installations  are  more 
complicated  in  the  number  of  parts;  they  use  a  more  cum- 
bersome heat  carrying  medium,   for  which  a  return  path  to 
the   boiler  must   be   provided;   and   have   parts,   in   the   form 
of   radiators,   which    occupy   valuable   room    space.     But   the 
steam   and    hot    water   plants    have    the    advantage    in    that 
their    circulations,    and    hence    their    transference    of    heat, 
are   quite   positive,  and   not  affected  by   wind  pressures.     A 
hot  water  or  a  steam  system  will  carry  heat  just  as  readily 
to  the  windward  side  of  a  house  as   it  will  to  the  leeward 
side,   a  point   which,   with   a   furnace   installation,   is   known 
to  be  quite  impossible.     F  urnace  heating,  on  the  other  hand, 
has   the    advantage    of    inherent    ventilation,    while    the    hot 
water  and  steam   systems,   as   usually   installed,   provide    no 
ventilation  except  that  due  to  air  leakage. 

61.  The  Parts  of  Hot  Water  and  Steam  Systems:— A  hot 

water  or  a  steam  system  may  be  said  to  consist  of  three 
principal  parts:  first,  the  boiler  or  heat  generator;  second, 
the  radiators  or  heat  distributors;  and  third,  the  connecting 
pipe-lines,  which  provide  the  circuit  paths  for  the  hot  water 
or  the  steam.  In  the  hot  water  system  it  is  essential  that 
the  heat  generator  be  located  at  the  lowest  point  in  the 
circuit,  for,  as  was  explained  in  Art.  5,  the  only  motive 
force  is  that  due  to  the  convection  of  the  water.  In  the 
steam  system  this  is  not  essential,  as  the  pressure  of  the 
steam  forces  it  outward  to  the  farthest  points  of  the  system. 
The  water  of  condensation  may  or  may  not  be  returned  by 
gravity  to  the  boiler.  Hence,  with  a  steam  system  a  radiator 
may  be  placed  below  the  boiler,  if  its  condensation  be  trapped 
or  otherwise  taken  care  of. 


74 


HEATING  AND  VENTILATION 


62.  Definitions: — In  speaking  of  the  piping  of  heating 
installations,  several  terms,  commonly  used  by  heating  en- 
gineers, should  be  thoroughly  understood.  The  large  pipes 
in  the  basement  connected  directly  to  the  source  of  heat, 
and  serving  as  feeders  or  distributors  of  the  heating  me- 
dium to  the  pipes  running  vertically  in  the  building,  are 
known  as  mains.  The  flow  mains  are  those  carrying^  steam 


Fig.  24. 


Pig.  21 


or  hot  water  from  the  source  of  heat  towards  the  radiators, 
and  the  return  mains  are  those  carrying  water  or 
condensation  from  the  radiators  to  the  source  of 
heat.  Those  vertical  pipes  in  a  building  to  which 
the  radiators  are  directly  connected  are  called  risers, 
while  the  short  horizontal  pipes  from  risers  to  radi- 
ators are  usually  termed  riser  arms.  As  there  are  flow 
mains  and  return  mains,  so  also,  there  are  flow  risers  and 
return  risers.  A  radiator  should  have  at  least  two  tappings, 
one  below  for  the  entry  of  the  heating  medium,  and  one 
on  the  end  section  opposite,  near  the  top  for  air  discharge 
as  shown  by  the  connected  steam  radiator  of  Fig.  24.  It 
may  have  three,  a  flow  tapping  and  a  return  tapping  at  the 
bottom  of  the  two  end  sections,  and  the  third  or  air  tapping 
near  the  top  of  the  end  section  at  the  return  end  as  shown 
by  the  connected  hot  water  radiator  of  Fig.  25.  A  return 


HOT    WATER    AND    STEAM    HEATING 


75 


main  traversing  the  basement  above  the  water  line  of  the 
boiler  is  designated  as  a  dry  return  and  carries  both  steam 
and  water  of  condensation;  one  in  such  position  below  the 
water  line  as  to  be  filled  with  water  is  designated  a  wet 
return,  and  the  returns  of  all  two-pipe  radiators  connecting 
with  wet  returns  are  said  to  be  sealed. 

63.  Classification: — One  classification  of  hot  water  and 
steam  systems  is  based  upon  the  position  and  manner  in 
which  the  radiators  are  used.  The  system  which  is,  per- 
haps, most  familiar  is  the  one  wherein  radiators  are  placed 
directly  within  the  space  to  be  heated.  This  heating  is  ac- 


Fig.  26. 


Big.  27. 


complished  by  direct  radiation  and  by  air  convection  cur- 
rents through  the  radiators,  no  provision  being  made  for  a 
change  of  air  in  the  room.  This  is  known  as  the  direct 
system,  and,  while  it  causes  movements  of  the  air  in  the 
room,  it  produces  no  real  ventilation.  See  Fig.  26. 

In  the  direct-indirect  system,  the  radiator  is  also 
placed  within  the  space  or  room  to  be  heated,  but  its  lower 
half  is  so  encased  and  connected  to  the  outside  of  the  build- 


HEATING  AND  VENTILATION 


ing  that  fresh  air  is  continually  drawn  up  through  the 
radiator,  is  heated,  and  thrown  out  into  the  room  as  sfoown 
by  Fig1.  27.  Thus  is  established  a  ventilating  system  mor^ 
or  less  effective. 

In  the  purely  indirect  system,  Fig.  28,  'the  radiating  sur- 
face is  erected  somewhere  remote  from  the  rooms  to  be 
neated,  and  ducts  carry  the  heated  air  from  the  radiator 
to  the  rooms  either  by  natural  convection,  as  in  some  in- 
stallations, or  by  fan  or  blower  pressure,  as  in  others. 
When  all  the  radiation  for  an  entire  building  is  installed 


Fig.   28. 


together  in  one  basement  room,  and  each  room  of  the  build- 
ing has  carried  to  it,  its  share  of  heat  by  forced  air  through 
ducts  from  one  large  centralized  fan  or  blower,  the  system 
is  called  a  Plenum  System,  and  is  given  special  consideration 
in  Chapters  IX  to  XL 

64.  A  second  classification  of  steam  and  hot  water  sys- 
tems is  made  according  to  the  method  of  pipe  connection 
between  the  heat  generator  and  the  radiation.  That  known 
as  the  one-pipe  system,  Fig.  29,  is  the  simplest  in  construc- 
tion and  is  preferred  by  many  -for  the  steam  installations. 
As  the  name  indicates,  its  distinguishing  feature  is  the 
single  pipe  leading  from  the  source  of  heat  to  the  radiator, 
the  steam  and  the  returning  condensation  both  using  this 
path.  In  the  risers  and  connections,  the  steam  and  con- 
densation flow  in  opposite  directions,  thus  requiring  larger 
pipes  than  where  a  flow  and  a  return  are  both  provided. 
In  this  system  the  condensation  usually  flows  with  the 
steam  in  the  main,  and  not  against  it,  until  it  reaches  such 
a  point  that  it  may  be  dripped  to  a  separate  return 
and  then  led  to  the  boiler.  In  the  so-called  one-pipe 
hot  water  system,  radiators  have  two  tappings  and  two 
risers,  but  the  flow  riser  is  tapped  out  of  the  top  of  the 


HOT    WATER    AND    STEAM    HEATING 


77 


Fig.   29. 

single  basement  main,  while  the  return  riser  is  tapped  into 
the  bottom  of  that  same   main  by  either  of  the   special  fit- 
tings shown  in  section  in  Fig.   30.     The  theory  is  that  the 
hot     water     from     the     boiler     travels 
along   the   top   of    the   horizontal    base- 
ment main,  while  the  cooler  water  from 
the  radiators  travels  along  the  bottom 
of   this    same   main.      Hence   the    neces- 
sity for  tapping  flow  risers   out  of  the 
top   and   return   risers   into   the   bottom 
of   this    main,    thus   avoiding   a    mixing 
of  the  two  streams.     Where  mains  are 
short    and    straight    as    in    the    smaller 
Pig-.  30.  residence      installations,      this      system 


78  HEATING  AND  VENTILATION 

seems  to  give  satisfaction;  but  it  is  very  evident  that,  where 
basement  mains  are  long  and  more  complicated,  a  mixing 
©f  the  two  streams  is  unavoidable,  thus  rendering  the  sys- 
tem unreliable. 

The  two-pipe  system  is  used  on  both  steam  and  hot 
water  installations.  For  steam  work  it  is  probably  no 
better  than  the  one-pipe  system  but  for  hot  water  work  it 
is  much  preferred.  In  this  system  two  separate  and  dis- 
tinct paths  may  be  traced  from  any  radiator  to  the  source 
of  heat."  In  the  basement  are  two  mains,  the  flow  and  the 
return,  and  the  risers  from  these  are  always  run  in  pairs, 
the  flow  riser  on  one  side  of  a  tier  of  radiators,  the  return 
riser  on  the  other  side.  A  two-pipe  steam  system  must 
have  a  sealed  return.  Typical  two-pipe  main  and  riser  con- 
nections are  shown  in  E  ig.  31. 


Fig.  31. 


Fig.  32. 


65.  A  third  system,  known  as  the  attic  main,  or  Mills 
system,  has  found  much  favor  with  heating  engineers  in 
the  installation  of  the  larger  steam  plants  although  it  could 


HOT    WATER    AND    STEAM    HEATING  79 

be  applied  as  well  to  the  larger  iiot  water  plants.  The 
distinguishing-  feature,  when  applied  to  a  steam  system, 
is  the  double  main  and  single  riser,  so  arranged  that  the 
condensation  and  live  steam  flow,  in  the  same  direction. 
This  is  accomplished  by  taking  the  live  steam  directly  to 
the  attic  by  one  large  main,  which  there  branches,  as  need 
be,  to  supply  the  various  risers,  only  one  riser  being  used 
for  each  tier  of  radiators  and  the  direction  of  flow  of  both 
steam  and  condensation  in  risers  being  downward.  Hence, 
this  system  avoids  the  unsightliness  of  duplicate  risers,  as 
in  the  two-pipe  system,  and  avoids  the  disadvantage  of  the 
one-pipe  basement  system,  the  last  named  having  steam 
and  condensation  flowing  in  opposite  directions  in  the  same 
pipe.  Fig.  32  shows  two  common  methods  of  connecting 
risers  and  radiators  with  this  system. 

66.  Vacuum  Systems  for  Steam: — Most  commonly,  the 
systems  mentioned,  when  steam,  are  installed  as  the  so- 
called  low  pressure  systems,  which  term  indicates  an  abso- 
•  lute  pressure  of  about  18  pounds  per  square  inch  or  3Y2 
pounds  gage  pressure.  On  extensive  work,  it  has  been 
found  advantageous  to  install  a  vacuum  system  to  increase 
economy,  also  to  insure  positive  steam  circulation  by  prompt 
removal  of  condensation  through  vacuum  returns.  Even 
for  comparatively  small  residence  installations  vacuum  ap- 
plications of  various  kinds  are  becoming  common. 

Vacuum  systems  may  be  divided  into  two  classes,  ac- 
cording to  the  way  in  which  the  vacuum  is  maintained.  For 
comparatively  small  plants,  not  using  exhaust  steam,  the 
vacuum  is  maintained  by  mercury  seal  connections,  and 
these  plants  are  usually  referred  to  as  mercury  seal  vacuum 
systems.  These  mercury  seals  may  be  attached  to  any 
standard  one  or  two-pipe  system  by  merely  replacing  the 
ordinary  air  valve  by  a  special  connection,  which  in  real- 


81) 


HEATING  AND  VENTILATION 


ity   is   only   a   barometer.      An   iron   tube,    Fig.    33,   dips   just 
below  the  surface   of  the  mercury  in  the  well   on  the   floor, 
and   extends   vertically  to  the   radiator  air   tap- 
ping   to    which    the    tube    connects    by    a    fitting 
which  will   allow   air  to   pass  into  and   through 
the    barometer,    but    will    not    allow    steam    to 
pass.      When    the    system    is    first    fired    up    and 
steam  is  raised  to  several   pounds  gage,  the  air 
leaves    all    the    radiators    by    bubbling    through 
the    mercury    seal    at    the    end    of    the    vertical 
iron  tube.     If  the  fire  is  then  allowed  to  go  out, 
the  steam  will  condense,  and  produce  an  almost 
perfect   vacuum    in   the   entire   system,    provided 
all    pipe    fitting   has   been   carefully   done.      This 
system   may    be    operated   as    a    vacuum    system 
at    4    or    5    pounds    absolute    pressure    and    have 
the  water  boiling  as  low  as  150  to   160  degrees. 
The    flexibility    of    this    system    recommends    it 
highly.      Applied    to    a    residence    or    store,    the 
plant  may   be   operated  during   the  day  at   sev- 
eral   pounds    gage    pressure,    if    necessary,    but 
when  fires  are   banked   for  the  night,   steam  re- 
mains in  all  pipes  and  radiators  as  long  as  the 
temperature    of   the    water    does    not    fall    much 
below    150    degrees.      This    is    in    sharp    contrast 
with    the    ordinary   system,    where   steam   disap- 
pears  from   all    radiators   as  soon  as   the  water 
temperature     drops     below     212     degrees.       The 
promptness  with  which  heat  may  be  obtained  in  the  morn- 
ing is  noteworthy,  for,  if  the  vacuum  has  been  maintained, 
steam  will  begin  to  circulate  as  soon  as  the  water  has  been 
raised  to  about  150  degrees.     According  to   demands  of  the 
weather,    the    radiators    may    be    kept    at    any    temperature 
along   the   range   of   150   to    220   degrees,    thus    giving   great 
flexibility. 

Instead  of  having  a  barometric  tube  at  each  radiator, 
one  mercury  seal  may  be  supplied  in  the  basement,  and  the 
air  tappings  of  all  radiators  connected  to  the  top  of  the 
tube  by  ^4  inch  piping.  The  Trane  vacuum  system  is  usually 
so  installed,  and  is  an  excellent  example  of  this  vacuum 
type. 


I 


HOT    WATER    AND    STEAM    HEATING 


81 


67.  The  second  class  of  vacuum  systems  includes  those 
designed  especially  for  use  in  office  buildings,  and  where- 
in the  vacuum  is  maintained  by  an  aspirator,  exhauster  or 
pump  of  some  description.  This  exhauster  may  handle  only 
the  air  of  the  system,  that  is,  it  may  be  connected  only 
to  the  air  tappings  of  all  radiators,  as  in  the  Paul  system, 
Fig.  34,  or  the  exhauster  may  handle  both  air  and  con- 
densation and  be  connected  to  the  return  tappings  of  all 
radiators,  as  in  the  Webster  system,  Fig.  35.  The  Paul 


Fig.  34. 


Fig.  35. 


system  is  fundamentally  a  one-pipe  system,  using  exhaust 
cr  live  steam  and  maintaining  its  circulation  without  back 
pressure,  by  exhausting  each  radiator  at  its  air  tapping, 
and  also  exhausting  the  condensation  from  the  basement 
tank  in  which  it  has  been  collected  by  gravity.  For  an 
aspirator  this  system  uses  either  air,  steam,  or  hot  water, 
as  the  conditions  may  determine.  The  Webster  system  is 
fundamentally  a  two-pipe  system  and  exhausts  from  the 
radiators  both  the  air  and  water  of  condensation,  all  radi- 
ator returns  being-  connected  to  the  (usually)  steam  driven 
vacuum  pump.  These  systems  are  designed  to  use  both  exhaust 
and  live  steam,  and  hence  are  finding  wide  application  in  the 
modern  heating  of  manufacturing  plants.  See  also  Chapter 
XII. 


CHAPTER   VII. 

HOT  WATER  AND  STEAM  HEATING. 


RADIATORS,     BOILERS,     FITTINGS     AND     APPLIANCES- 

The  various  systems  just  described  are  merely  different 
ways  of  connecting  the  source  of  heat  to  the  distributors 
of  heat,  i.  e.,  methods  of  pipe  connections  between  heater 
and  radiators.  Many  forms  of  radiators  exist,  as  well  as 
many  types  of  heaters  and  boilers,  each  adapted  to  its  own 
peculiar  condition.  It  is  in  this  choice  of  the  best  adapted 
material  where  the  heating  engineer  shows  the  degree  of 
his  practical  training,  and  the  closeness  with  which  he  fol- 
lows the  latest  inventions,  improvements  and  applications. 

68.  Classification  as  to  Material: — Radiators  may  be 
classified,  according  to  material,  as  cast  iron  radiators, 
pressed  steel  radiators  and  pipe  coil  radiators.  Cast  radi- 
ators have  the  hollow  sections  cast,  as  one  piece,  of  iron. 
The  wall  is  usually  about  %  inch  to  %  inch  thick,  and  is 
finally  tested  to  a  pressure  of  100  pounds  per  square  inch. 
Sections  are  joined  by  wrought  iron  nipples  which,  at  the 
same  time,  serve  to  make  passageways  between  any  one 
section  and  its  neighbors  for  the  current  of  heating  me- 
dium, whether  of  steam  or  hot  water.  Cast  iron  radiators 
have  the  disadvantage  of  heavy  weight,  danger  of  break- 
ing by  freezing,  occupying  much  space,  and  having  a  com- 
paratively large  internal  volume,  averaging  a  pint  and  a 
half  per  square  foot  of  surface. 

Pressed  radiators  are  made  of  sheet  steel  of  No.  16 
gage,  and,  after  assembly,  are  galvanized  both  inside  and 
out.  Each  section  is  composed  of  two  pressed  sheets  that 
are  joined  together  by  a  double  seam  as  shown  at  a,  Fig. 
36,  which  illustrates  a  section  through  a  two-column  unit. 


Fig.   36. 

The  joints  between  the  sections  or  units  are  of  the  same 
kind.  It  is  readily  seen  that  such  construction  tends  to- 
ward a  very  compact  radiating  surface.  Pressed  radia- 


HOT     WATER    AND    STEAM    HEATING  83 

tors  are  comparatively  new,  but,  in  their  development, 
promise  much  in  the  way  of  a  light,  compact  radiation.  In 
comparison  with  the  cast  iron  radiators,  they  are  free  from 
the  sand  and  dirt  on  the  inside,  thus  causing  less  trouble 
with  valves  and  traps.  The  internal  volume  will  approxi- 
mate one  pint  per  square  foot  of  surface.  See  Fig.  37. 

Radiators  composed  of  pipes,  in  various  forms,  are 
commonly  referred  to  as  coil  radiators.  They  are  daily 
becoming  less  common  for  direct  and  direct-indirect  work, 
because  of  their  extreme  unsightliness.  Piping  is  still 
much  used  as  the  heat  radiator  in  indirect  and  plenum 
systems,  although  both  cast  and  pressed  radiators  are  now 
designed  for  both  of  these  purposes  where  low  pressure 
steam  is  used.  In  all  coil  radiator  work,  no  matter  for 
what  purpose,  1  inch  pipe  is  the  standard  size.  However, 
in  some  cases  pipes  are  used  as  large  as  2  inches  in  diam- 
eter. This  1  inch  pipe  is  rated  at  1  square  foot  of  heating 
surface  per  3  lineal  feet  and  has  about  1  pint  of  containing 
capacity  per  square  foot  of  surface. 

69.  Classification  as  to  Form: — Radiators  may  again  be 
classified  in  accordance  with  form,  into'  the  one,  two,  three, 
and  four-column  floor  types,  the  wall  type,  and  the  flue 
type.  See  Fig.  37.  These  terms  refer  only  to  cast  and 
pressed  radiators.  By  the  column  of  a  radiator  is  meant 
one  of  the  unit  fluid-containing  elements  of  which  a  sec- 
tion is  composed.  When  the  section  has  only  one  part  or 
vertical  division,  it  is  called  a  single-column  or  one-column 
type;  when  there  are  two  such  divisions,  a  two-column; 
when  three,  a  three-column;  and  when  four,  a  four- 
column  type.  What  is  known  as  the  wall  type  radiator  is 
a  cast  section  one-column  type  so  designed  as  to  be  of 
the  least  practicable  thickness.  It  presents  the  appear- 
ance, often,  of  a  heavy  grating,  and  is  so  made  as  to 
have  from  5  to  9  square  feet  of  surface,  according  to  the 
size  of  the  section.  One-column  floor  radiators  made  with- 
out feet  are  often  used  as  wall  radiators.  A  flue  radiator 
is  a  very  broad  type  of  the  one-column  radiator,  the  parts 
being  so  designed  that  the  air  entering  between  the  sections 
at  the  base  is  compelled  to  travel  to  the  top  of  the  sections 
before  leaving  the  radiator.  This  type  is  therefore  well 
adapted  to  direct-indirect  work.  See  Fig.  37. 


HEATING  AND  VENTILATION 


Stairway  Type    Dining  Room  Type    Flue  Type    Circular  Type 


CAST     RADIATORS 


Wall  Type 


Two-Column 
Type 


Three-Column 
Type 


Four-Column 
Type 


PRESSED     RADIATORS 


Single-Column     Two-Column 
Type  Type 


Three-Column 
Type 


Fig:.   37. 


Wall  Type 


HOT    WATER    AND    STEAM    HEATING  85 

Many  special  shapes  of  assembled  radiators  will  be 
met  with,  but  they  will  always  be  of  some  one  of  the  fun- 
damental types  mentioned  above.  For  instance,  there  are 
"stairway  radiators,"  built  up  of  'successive  heights  of 
sections,  so  as  to  fit  along  the  triangular  shaped  wall  under 
stairways;  there  are  "pantry"  radiators  built  up  of  sections 
so  as  to  form  a  tier  of  heated  shelves;  there  are  "dining 
room"  radiators  with  an  oven-like  arrangement  built  into 
their  center;  and  there  are  "window  radiators"  built  with 
low  sections  in  the  middle  and  higher  ones  at  either  end, 
so  as  to  fit  neatly  around  a  low  window.  Fig.  37  shows  a 
number  of  these  common  forms  as  used  in  practice. 


70.  Classification  as  to  Heating  Medium: — A  third  class- 
ification   of    radiators,    according    to    heating    medium    em- 
ployed,   gives    rise    to    the    terms    steam    radiator    and    hot 
water  radiator.     Casually,  one  would  notice  little  difference 
between  the  two,  but  in  construction  there  is  a  vital  differ- 
ence.     Steam   radiation   has   the    sections    joined   by    nipples 
along   the    bottom   only,    but   hot   water   radiation,  has   them 
joined  along  the  top  as  well.     This  is  quite  essential  to  the 
proper  circulation  of  the  water.     Steam  radiation  is  always 
tapped  for  pipe  connections  at  the  bottom.     Hot  water  rad- 
iation may  have  the   flow  connection  enter  at  the   top,   and 
the    return    connection    leave   at   the    bottom,    or    may    have 
both   connections   at  the   bottom.     Hot  water   radiation  can 
be   heated   very    successfully  with   steam,   but   steam    radia- 
tion cannot  be  used  with   hot  water. 

71.  High  versus  JLow  Radiators: — In  the  adoption  of  a 
radiator  height,   the  governing  feature  is  usually  the  space 
allowed  for  the   radiator.     Thus,   if  a  radiator  of  26   inches 
in  height  requires  so  many  sections  as  to  become  too  long, 
then  a  32  inch  or  a  38  inch  section  may  be  taken.     In  gen- 
eral,   however,    low    radiators    should    be    used    as    far    as 
possible,  for,  with  a  high  radiator,  the  air  passing  up  along 
the  sides  of  the  sections  becomes  heated  before  reaching  the 
top,  and  therefore,   receives  less   heat   from  the  upper  half 
of    the    radiator,    since    the    temperature    difference    here    is 
small.      Hence,   the   statement   that  low  radiators  are   more 
efficient,    that    is,    will    transmit   more    B.    t.    u.    per    square 
foot  per  hour  than  will  the   high   radiators. 


86 


HEATING  AND  VENTILATION 


72.  Effect  of  Condition  of  Radiator  Surface  on  the 
Transmission  of  Heat: — The  efficiency  of  a  radiator  depends 
very  largely  upon  the  condition  of  its  outer  surface,  a 
rough  surface  giving  off  very  much  more  heat  than  a 
smooth  surface.  Painting,  bronzing,  shellacing  or  cover- 
ing the  radiator  in  any  manner  affects  the  ability  of  the 
radiator  to  impart  heat  to  the  air  circulating  around  it. 
Various  tests  bearing  upon  this  question  have  been  con- 
ducted, agreeing  fairly  well  in  general  results.  A  series 
of  tests  conducted  by  Prof.  Allen  at  the  University  of 
Michigan,  indicated  that  the  ordinary  bronzes  of  copper, 
zinc  or  aluminum  caused  a  reduction  in  the  efficiency  below 
that  of  the  ordinary  rough  surface  of  the  radiator  of 
about  25  per  cent.,  while  white  zinc  paint  and  white  enamel 
gave  the  greatest  efficiency,  being  slightly  above  that  of 
the  original  surface.  Numerous  coats  of  paint,  even  as  high 
as  twelve,  seemed  to  affect  the  efficiency  in  no  appreciable 
manner,  it  being  the  last  or  outer  coat  that  always  de- 
termined at  what  rate  the  radiator  would  transmit  its  heat. 

TABLE  X. 
Dimensions  and  Surfaces  of  Radiators,  per  Section. 


•si 

0    g 

•"•g 

Radiator  Heights. 

Type  of 
Radiator 

IS 

1  = 

0  — 

I 

*1 

as  'H 

45" 

44" 

38" 

82" 

26" 

23" 

22" 

20" 

18" 

16" 

14" 

53 

lOol.  O.  I  

5 

3 

3 

2% 

2 

1% 



1% 

2  Ool.  O.  I  

8 

8 

5 



4 

8>i 

2% 

2% 

2 

8  Ool.  O.I  

9% 

3 

.... 

6 

5 

4% 

3K 

— 

3 



2% 

4  Ool  O   I. 

,. 

-,/ 

QT/ 

8 

gi/ 

5 

4 

8 

19* 

3 

7 

8 

5 

4 

6 

424 

4 

1  Ool  Press  .  . 

4 

ls/n 

I'K 

1 

X 

2  Ool  Press 

2 

4 

2Ji 

9 

3  Ool  Press 

2% 

5M 

4^ 

94 

1  Ool.  Wall 

1 

Pressed 

73.  Amount  of  Surface  Presented  by  Various  Radiators: — 

Table    X,    gives,    according    to    the    columns    and    heights, 


HOT    WATER    AND    STEAM    HEATING  87 

the  number  of  square  feet  of  heating  surface  per  section 
in  cast  and  pressed  radiators.  This  table  will  be  found  to 
present,  in  very  compact  form,  the  similar  and  much  more 
extended  tables  in  the  various  manufacturers'  catalogs. 
An  approximate  rule  supplementing  this  table  and  giving, 
to  a  very  fa^r  degree  of  accuracy,  the  square  feet  of  aur- 
face  in  any  standard  radiator  section,  is  as  follows:  mul- 
tiply the  height  of  the  section  in  inches  by  the  number  of 
columns  and  divide  by  the  constant  20.  The  result  is  the 
square  feet  of  radiating  surface  per  section.  The  rule  ap- 
plies with  least  accuracy  to  the  one  column  radiators. 

74.  Hot  Water  Heaters: — Heaters  for  supplying  the  hot 
water  to  a  heating  system  may  be  divided  into  three  classes: 
— the  round  vertical,  for  comparatively  small  installations; 
the  sectional,  for  plants  of  medium  size;  and  the  water  tube 
or  flre  tube  heater  with  brick  setting  for  the  larger  in- 
stallations and  for  central  station  work.  The  round  and 
sectional  types  usually  have  a  ratio  between  grate  and 
heating  surface  of  1  to  20,  while  the  water  tube  or  fire  tube 
heater  will  have,  as  an  average,  1  to  40.  Many  different 
arrangements  of  heating  surface  are  in  use  to-day,  every 
manufacturer  having  a  product  of  particular  merit.  Trade 
catalogs  supply  the  most  up-to-date  literature  on  this 
subject,  but  cuts  of  each  of  the  types  mentioned  above  may 
be  found  in  Pig.  38. 

75..  Steam  Boilers: — The  products  of  many  manufac- 
turers show  but  little  difference  between  the  hot  water 
heater  and  the  steam  boiler.  The  latter  is  usually  supplied 
with  a  somewhat  larger  dome  to  give  greater  steam  stor- 
age capacity.  For  heating  purposes,  steam  boilers  fall 
into  the  same  three  classes  as  mentioned  under  water  heat- 
ers, having  about  the  same  ratio  of  heating  surface  to  grate 
surface.  With  the  steam  boiler  generating  steam  at,  say, 
5  pounds  gage,  the  temperature  on  one  side  of  the  heating 
surface  is  about  227  degrees,  while  in  a  water  heater  the 
temperature  on  the  same  side  is  about  180  degrees.  Hence, 
with  the  same  temperature  of  the  burning  gases,  the  tem- 
perature difference  is  greater  in  a  water  heater  than  in  a 
boiler,  resulting  in  a  more  rapid  transfer  of  heat,  and  a 
correspondingly  greater  efficiency. 

76.  Combination  Systems: — What  are  known  as  com- 
bination systems  are  frequently  used,  principally  the  one 


HEATING  AND  VENTILATION 


which  combines  warm  air  heating  with  either  steam  or 
hot  water.  For  such  a  system  there  is  needed  a  combina- 
tion heater,  as  shown  in  Fig.  19.  It  consists  essentially  of  a 
furnace  for  supplying  warm  air  to  some  rooms,  the  down- 
stairs of  a  residence,  for  instance,  and  contains  also  a  coil 


Fire  Tube  Type 
Fig.  38. 


HOT    WATER    AND    STEAM    HEATING  89 

for  furnishing  hot  water  to  radiators  located  in  other  rooms, 
say,  on  the  upper  floors,  or  in  places  where  it  would  be 
difficult  for  air  to  be  delivered.  Considerable  difficulty  has 
been  encountered  in  properly  proportioning  the  heating  sur- 
face of  the  furnace  to  that  of  the  hot  water  heater,  and  the 
systems  have  not  come  into  general  use. 

77.  Fittings: — Common  and  Special: — Couplings,  elbows 
and  tees,  especially  for  hot  water  work,  should  be  so  formed 
as  to  give  a  free  and  easy  sweep  to  the  contents.  It  is 
highly  desirable  in  hot  water  work  to  use  pipe  bends  of  a 
radius  of  about  five  pipe  diameters,  instead  of  the  common 
elbow.  In  either  case  all  pipe  ends  should  be  carefully 
reamed  of  the  cutting  burr  before  assembling.  This  is 
most  important,  as  the  cutting  burr  is  sometimes  heavy 
enough  to  reduce  the  area  of  the  pipe  by  one-half,  thus 
creating  serious  eddy  currents,  especially  at  the  elbows. 
If  the  single  main  hot  water  system  be  installed,  great 
care  should  be  used  to  plan  the  mains  in  the  shortest  and 
most  direct  routes,  and  the  special  fittings  described  and 
shown  in  Art.  64  should  be  used. 

What  are  known  as  eccentric  reducing  fittings  are  often 
of  value  in  avoiding  pockets  in  steam  lines.  Fig.  39  shows 


Fig.   39. 

types  of  these,  which  should  always  be  used  when,  by  re- 
duction or  otherwise,  a  horizontal  steam  pipe  would  pre- 
sent a  pocket  for  the  collection  of  condensation  with  its  re- 
sultant water  hammer. 

Valves  for  either  steam  or  hot  water  should  be  of  the 
gate  pattern  rather  than  the  globe  pattern.  The  latter  is 
objectionable  in  hot  water  systems  because  of  the  resistance 
offered  the  stream  of  water,  due  to  the  fact  that  the  axis 
of  the  valve  seat  opening  is  perpendicular  to  the  axis  of 
the  pipe  connected.  The  globe  valve  is  objectionable  in  a 
steam  system  because  of  the  fact  that  in  a  horizontal  run 


90 


HEATING  AND  VENTILATION 


of  pipe  it  forms  very  readily  a  pocket  for  the  collection 
of  condensation,  thus  often  producing  a  source  of  water 
hammer.  In  every  way  gate  valves  are  preferable,  for,  as 
shown  in  Fig.  40,  they  present  a  free  opening'without  turns. 

The  same  caution  applies 
in  the  use  of  check  valves. 
Swing  checks  should  al- 
ways be  specified  rather 
than  lift  checks,  for  the 
former  offer  much  less  re- 
sistance to  the  passage  of 
the  hot  water,  or  the 
steam  and  condensation,  as 
the  case  may  be.  P  ig.  41 


Fig.  40. 


shows    a    lift    check    and    a 
swing  check. 

To  avoid  the   annoyance   so  often  experienced  by  leaky 
packing  around  valve  stems,  there  have  been  designed  and 


Fig.   41. 

placed    on    the    market    various    forms    of    packless    valves. 
These  are  to  be   especially  recommended  for  vacuum  work, 
as  the  old  style  valve  with  its  packed  stem  is,  perhaps,  the 
cause   of   more  failures  of  vacuum   systems 
than  any  other  one  item.     Fig.   42  shows  a 
section    of    this    type    of    valve    using    the 
diaphragm  as  the  flexible   wall.     All   pack- 
less    valves    will    be    found    to    use    a    dia- 
phragm of -one   form   or  another. 

Quick  -  opening       Valves,       or       butterfly 
valves,  are  much  used  on  hot  water  radi- 
ators;   one   quarter  turn    of   the   wheel    or 
handle  provided  serves  to  open  these  full 
Fig.  42.  and,  when  closed,  they  are  so  arranged  that 


HOT    WATER    AND    STEAM    HEATING 


91 


a  small  hole  through  the  valve  permits  just  enough  leakage 
to  keep  the  radiator  from  freezing.  Special  radiator  valves 
for  steam  are  also  to  be  obtained. 

Air  valves  have  a  most  important  function  to  discharge. 
As    the   air   accumulates   above   the   water   or    steam   in   the 


Fig.   43. 


radiators,  its  removal  becomes  absolutely  necessary,  if  all 
of  the  radiating  surface  is  to  remain  effectual.  For  this 
purpose  small  hand  valves  or  pet  cocks,  Fig.  43,  are  in- 
serted near  the  top  of  the  end  section  in  all  hot  water 
work;  and  either  these  same  valves  or  automatic  ones  are 
inserted  for  steam  work.  Valves  are  not  as  essential  on 
two-pipe  steam  systems  as  on  water  or  single-pipe  steam 
systems,  yet  are  generally  used.  For  steam  the  air  valve 
should  be  about  one-third  the  radiator  height  from  the  top. 

Fig.  44  shows  a  common  type 
of  automatic  air  valve  using  the 
principle  of  the  expansion  stem.  As 
long  as  the  air  flows  around  the 
stem  and  exhausts,  the  stem  re- 
mains contracted,  and  the  needle 
valve  open;  but  when  the  hot  steam 
enters  and  flows  past  the  expansion 

stem,  it  lengthens  sufficiently  to  close  the  needle  valve.  In 
other  forms  of  air  valves  the  heat  of  the  steam  closes  the 
needle  valve  by  the  expansion  of  a  volatile  liquid  in  a  small 
closed  retainer.  In  still  other  forms  the  lower  part  of  the 
valve  casing  is  filled  with  water  of  condensation  upon 
which  floats  an  inverted  cup,  having  air  entrapped  within. 
This  cup  carries  the  needle  of  the  valve  at  its  upper  ex- 
tremity, the  heat  of  the  steam  expanding  the  air  sufficiently 
to  raise  the  cup  and  close  the  valve.  Where  the  system  Is  de- 
signed to  act  as  a  gravity  installation,  special  air  valves  must 
be  used  which  will  not  allow  air  to  enter  at  any  time.  Fig. 


92  HEATING  AND  VENTILATION 

45  shows  a  type  of  automatic  valve  designed  to  accommo- 
date larger  volumes  of  air  with  promptness, 
as  when  a  long  steam  main  or  large  trap  is 
to  be  vented.  This  type  employs  a  long  cen- 
tral tube,  as  shown,  which  carries  at  the  top 
the  valve  seat  of  the  needle  valve.  The 
needle  itself  is  carried  by  the  two  side  rods. 
As  long  as  the  air  flows  up  through  the 
central  pipe,  the  needle  valve  will  remain 
open;  but  when  hot  steam  enters  the  tube, 
it  expands,  and  carries  the  valve  seat  up- 
ward against  the  needle,  thus  closing  the 
valve.  The  size  and  strength  of  parts  makes 
this  form  a  very  reliable  one. 

The  expansion  tank,  Fig.  46,  for  a  hot  wat- 
er system  is  often  located  in  the  bath  room  or 
closet  near  the  bath  room  and  its  overflow 
connected  to  proper  drainage.  It  should  be 
at  least  2  feet  above  the  highest  radiator. 
The  connection  to  the  heating  system  mains 
is  most  often  by  a  branch  from  the  nearest 
radiator  riser,  or  it  may  have  an  independ- 
ent riser  from  the  basement  flow  main.  The 
capacity  of  the  tank  is  usually  taken  at 
about  one-twentieth  of  the  volume  of  the 
entire  system,  or  a  more  easily  applied  rule 
is  to  divide  the  total  radiation  by  40  to  ob- 
tain the  capacity  of  the  tank  in  gallons. 


Fig.  45. 


See  Table  33,  Appendix. 


Figr.    46. 


CHAPTER  VIII. 


HOT  WATER  AND  STEAM  HEATING. 


PRINCIPLES    OF    THE   DESIGN,    WITH    APPLICATION. 

In  a  hot  water  or  steam  system,  the  first  important 
item  to  be  determined  by  calculation  is  the  amount  of 
radiation,  in  square  feet,  to  be  installed  in  each  room. 
Nearly  all  other  items,  such  as  pipe  sizes,  boiler  size,  grate 
area,  etc.,  are  estimated  with  relation  to  this  total  radia- 
tion to  be  supplied.  The  correct  determination,  then,  of 
the  square  feet  of  radiation  in  these  systems  is  all-im- 
portant. 

78.  Calculation  of  Radiator  Surface: — Considering  the 
standard  room  of  Chapter  III,  where  the  heat  loss  was  de- 
termined to  be  14000  B.  t.  u.  per  hour  on  a  zero  day,  the 
problem  is,  to  find  what  amount  of  surface  and  what  size  of 
radiator  will  deliver  to  the  room,  under  the  conditions  as 
given,  just  about  14000  B.  t.  u.  per  hour.  Experiments  by 
numerous  careful  investigators  have  shown  that  the  ordin- 
ary cast  iron  radiator,  located  within  the  room  and  sur- 
rounded with  comparatively  still  air,  gives  off  heat,a,t  the 
rate  of  1.7  "B.  t.  u.  (1.6  to  1.8,  or  1.7  averag&)  per  tfegree 
difference  between  the  temperature  of  the  surrounding  air 
and  the  average  temperature  of  the  heating  medium,  per 
hour.  This  is  called  the  rate  of  transmission.  With  hot 
water  the  average  conditions  within  the  radiator  have 
been  found  to  be  as  follows:  temperature  of  the  water  en- 
tering the  radiator  180  degrees;  leaving  the  radiator  160 
degrees;  hence,  the  average  temperature  at  which  the  in- 
terior of  the  radiator  is  maintained  is  170  degrees.  Since, 
in  this  country,  the  standard  room  temperature  is  70  de- 
grees, and,  for  hot  water,  the  "degree  difference"  is  170  — 
70  =  100,  then  a  hot  water  radiator  will  give  off  under 
standard  conditions  1.7  X  100  =  170  B.  t.  u.  per  hour.  The 
temperature  within  a  steam  radiator  carrying  steam  at 
pressures  varying  between  2  and  5  pounds  gage  is  usually 
taken  at  220  degrees,  and  the  total  transmission  is  approx- 
imately 1.7  X  (220  —  70)  =  255  B.  t,  u.  per  square  foot  per 


94  HEATING  AND  VENTILATION 

hour.  The  general  formula  for  the  square  feet  of  radiation, 
then,  is 

R  _         Total  B.  t.   u.  lost  from  the  room  per  hour 

1.7  (Temp.  diff.  between  inside  and  outside  of  rad.) 

For  hot  water,  direct  radiation  heating,  this  becomes,  to  the 
nearest  thousandth 

H 

Rw  =  —   .006  H  (30) 

1.7   (170  —  70) 

For  steam,  direct  radiation 

H 

R*  = —    .004  H  (31) 

1.7  (220  —  70) 

It  will  be  noticed  from  (30)  and  (31)  that  Rw  =  1.5  RB  which 
accounts  for  the  practice  that  some  people  have  of  finding 
all  radiation  as  though  it  were  steam,  and  then,  when  hot 
water  radiation  is  desired,  adding  50  per  cent,  to  this 
amount. 

APPLICATION. — From  the  standard  room  under  considera- 
tion, formula  30  gives  Rw  —  .006  X  14000  =  84  square  feet 
of  radiator  surface  for  hot  water;  and  formula  31  gives  R$ 
=  .004  X  14000  =  56  square  feet  of  radiator  surface  for 
steam.  From  these  values  the  number  of  sections  of  a  giv- 
en type  of  radiator  can  be  determined  by  dividing  by  the 
area  of  one  section,  as  explained  in  the  preceding  chapter. 
The  length  of  the  radiator  may  also  be  found  from  this 
same  table,  by  noting  the  thickness  of  the  sections,  and 
multiplying  by  their  number. 

Formulas  30  and  31  give  the  standard  ratios  be- 
tween the  heat  loss  and  direct  radiation.  If,  however,  the 
radiation  is  installed  as  direct-indirect,  it  is  quite  common 
practice  to  increase  the  amount  of  direct  radiation  by  25 
per  cent,  to  allow  for  the  ventilation  losses.  On  this  basis 
formulas  30  and  31  become,  respectively, 

Rw  =   .0075  H  (32) 

R8  =   .005     H  (33) 

Duct  sizes  for  properly  accommodating  the  air  in  direct- 
indirect  heating  may  be  taken  from  the  following.  To  ob- 
tain the  duct  area  in  square  inches,  multiply  the  square 
feet  of  radiation  by  .75  to  1  for  steam,  and  by  .5  to  .75 
for  hot  water.  To  obtain  the  amount  of  air  which  may  be 
expected  to  enter  and  pass  through  the  radiator  into  the 


HOT    WATER    AND    STEAM    HEATING  95 

room,  multiply  the  square  feet  of  radiation  by  100  for 
steam,  or  by  75  for  hot  water.  This  gives  the  cubic  feet  of 
air  entering  per  hour. 

Again,  if  the  radiation  is  installed  as  purely  indirect, 
yet  not  as  a  plenum  system,  it  is  common  to  increase  the 
amount  of  direct  radiation  by  50  per  cent.  Now  formulas 
30  and  31  become,  respectively, 

Rw  =  .009  H  (34)-a 

Ra  =   .006  H  (34)-b 

F  or  proportioning  the  duct  sizes  in  indirect  heating 
use  the  following  table.  To  obtain  the  duct  area  in  square 
inches,  multiply  the  square  feet  of  radiation  installed  by 

Steam  Hot  Water 

First  Floor  1.5  to  2.0  1.0     to  1.33 

Second   Floor  1.0  to  1.25  .66  to      .83 

Other  Floors  .9  to  1.0  . 6     to      .66 

Vent  ducts,  where  provided,  are  usually  taken  .8  of  the 
area  of  supply  ducts.  Also,  for  finding  the  amount  of  air  in 
cubic  feet,  which  may  be  reasonably  expected  to  enter 
under  these  conditions,  Carpenter  gives  the  following: 
Multiply  the  square  feet  of  indirect  radiation  by 

Steam  Hot  Water 
First    Foor                        200  150 

Second   Floor  170  130 

Other  Floors  150  115 

If  this  amount  of  air  is  insufficient  for  the  desired  degree 
of  ventilation,  more  air  must  be  brought  in  by  correspond- 
ingly larger  ducts,  and  for  each  300  cubic  feet  additional 
with  steam,  or  each  200  cubic  feet  additional  with  hot 
water,  add  one  square  foot  to  the  radiation  surface. 

A  steam  system  may  be  installed  to  work  at  any  pres- 
sure, from  a  vacuum  of,  say,  10  pounds  absolute,  to  as  high 
a  pressure  as  75  pounds  absolute.  To  calculate  the  prop- 
er radiation  for  any  of  these  conditions  use  formula  31  or 
its  derivatives,  and  substitute  the  proper  steam  tempera- 
ture in  place  of  220  degrees. 

In  like  manner,  to  find  the  amount  of  hot  water  radi- 
ation for  any  other  average  temperatures  of  the  water 
than  the  one  given,  merely  substitute  the  desired  average 


96  HEATING  AND  VENTILATION 

temperature  in  the  place  of  170.  One  point  should  be  re- 
membered, the  maximum  drop  in  temperature  as  the  water 
passes  through  the  heater  will  seldom  be  more  than  20 
degrees,  even  under  severe  conditions.  More  often  it  will 
be  less,  but  this  value  is  used  in  calculations.  Again,  the 
temperature  of  the  entering  water  may  be  at  the  boiling 
point,  if  necessary,  thus  causing  each  square  foot  of  sur- 
face to  be  more  efficient  and  consequently  reducing  the  to- 
tal radiation  in  the  room.  To  illustrate,  try  formula  30 
with  a  drop  in  temperature  from  210  to  190  degrees  and  find 
64  square  feet  of  radiator  surface  for  this  room.  Since  a 
radiator  always  becomes  less  efficient  from  continued  use,  it 
is  best  to  design  a  system  with  a  lower  temperature  as 
given  in  the  formula,  and  then,  if  necessary  under  stress 
of  conditions,  this  system  may  be  increased  in  capacity  by 
increasing  the  water  temperature,  say,  up  to  the  boiling 
point. 

79.  Empirical  Formulas: — All  of  the  above  formulas  may 
be  considered  as  rational  and  checked  by  years  of  experience 
and  application.  Many  empirical  formulas  have  been  de- 
vised in  an  attempt  to  simplify,  but  the  results  are  always 
so  untrustworthy  that  the  rules  are  worthless  unless  used 
with  that  discretion  which  comes  only  after  years  of  prac- 
tical experience.  Many  of  these  rules  are  based  on  the 
cubic  feet  of  volume  heated,  without  any  other  allowance, 
these  being  given  anywhere  from  one  square  foot  of  steam 
surface  per  30  cubic  feet  of  space,  to  one  square  foot  to 
100  cubic  feet.  The  extreme  variation  itself  shows  the  un- 
reliableness  of  this  method,  and  under  no  conditions  should 
it  be  used  for  proportioning  radiating  surface.  Various 
central  heating  companies,  and  others,  proportion  radia- 
tors for  their  plants  according  to  their  own  formulas, 
among  which  the  following  may  be  noted. 

GWG  G        W  C 

(a)  Rw  = 1- 1 R*  = 1- h  

2         10          60  2          10  200 

2 

(b)  Rw  =  G  +  .05  W  +  .01  C      R»  =  —  (G  +  .05  W  +  .01  (?) 

(c)  Rv>  =  .75  G  +  .10  W  +  .01  C      Rs  =  .5  G  +  .05  W  +  .005  C 

It  is  evident  that  these  are  really  simplified  forms  of  Car- 
penter's original  formula.  When  applied  to  the  sitting 
room,  where  Carpenter's  formula  gave,  for  hot  water  and 


HOT    WATER    AND    STEAM    HEATING  97 

steam,  84  square  feet  and  56  square  feet,  respectively,  (a) 
gives  85.5  and  63,  (b)  gives  75  and  50,  and  (c)  gives  82.5 
and  46  respectively. 

Another  approximate  rule  devised  by  John  H.  Mills 
and  still  used  to  some  extent  is  "Allow  1  square  foot  of 
steam  radiation  for  every  200  cubic  feet  of  volume,  1  square 
foot  for  every  20  square  feet  of  exposed  wall  and  1  square 
foot  for  every  2  square  feet  of  exposed  glass."  Applying 
this  to  the  standard  room,  it  gives  9.75  -f-  13.25  +  18  =  41 
square  feet  of  steam  radiation  as  against  56  square  feet 
by  rational  formula.  This  shows  a  considerable  difference 
from  the  rules  preceding. 

80.  Greenhouse  Radiation: — The  problem  of  properly 
proportioning  greenhouse  radiation  is  considered,  by  some 
of  such  special  nature  as  to  prohibit  the  use  of  theoretical 
formulas.  The  fact  that  the  glass  area  is  so  large  compared 
to  the  wall  area  and  the  volume,  combined  with  the  fact 
that  the  head  of  water  in  the  system  is  small  and  that  the 
radiation  surface  is  usually  built  up  as  coils  from  1&,  1%  or 
2  inch  wrought  iron  pipe,  gives  rise  to  a  problem  that  differs 
essentially  from  that  of  a  room  of  ordinary  construction.  It 
is  not  surprising,  therefore,  to  find  a  great  variety  of  empir- 
ical formulas  designed  exclusively  for  this  work.  Whatever 
merit  these  may  have,  they  do  not  give  the  assurance  that 
comes  from  the  application  of  rational  formulas.  It  is  always 
best  to  use  rational  formulas  first  and  then  check  by  the 
various  empirical  methods. 

Formulas  30  and  31,  stated  in  Art.  78,  when  properly 
modified,  are  applicable  to  greenhouses  and  give  very  re- 
liable results.  As  stated  above,  the  radiating  surface  Is 
usually  that  of  wrought  iron  pipes  hung  below  the  flower 
benches  or  along  the  side  walls  below  the  glass.  The  trans- 
mission constant,  K,  for  wrought  iron  or  mild  steel  is  2.0  to 
2.2  B.  t.  u.  per  square  foot  per  degree  difference  per  hour, 
making  the  total  transmission  per  square  foot  of  coil  surface 
per  hour  about  2(170  —  70)  =  200  for  hot  water,  and  2(220 
—  70)  =  300  for  steam.  These  values  may  be  safely  used. 
The  only  necessary  modification  of  the  two  formulas  men- 
tioned, consists  in  replacing  the  constant  1.7  by  2,  giving 
for  hot 


98  HEATING  AND  VENTILATION 


=   .005  H  (3»)-a 


2(170  —  70) 
And  for  steam 

H 

R,  —  =   .0033  H  (35)-b 

2(220  —  703 

If,  however,  the  highest  temperature  at  which  it  is  desirable 
to  maintain  the  house  in  zero  weather  is  other  than  70  de- 
grees, this  temperature  should  be  used  instead  of  70. 

In  a  greenhouse  there  is  very  little  circulation  of  air, 
hence  the  heat  loss.  H,  would  be  found  from  the  equivalent 
glass  area  i.  e.,  (G  +  .25  TF).  Formula  (35)-a  and  b  would 
then  reduce  to  Rw  =  .35  (G  +  .25  TF)  and  Rs  =  .23  (G  +  .25  TF). 
Because  of  the  fact  that  the  heat  loss  through  the  wall  is 
very  small  compared  to  that  through  the  glass,  some  per- 
sons prefer  to  drop  the  last  term  entirely.  If  this  is  done  the 
simple  relations,  Rw  =  .35  G,  and  Ra  —  .23  G,  will  be  obtained 
for  a  greenhouse  of  maximum  temperature  of  70  degrees.  It 
is  noticed  that  these  values  give  about  one  square  foot  of  H.  TF. 
radiation  to  three  square  feet  of  glass  area,  and  one  square  foot  of 
steam  radiation  to  five  square  feet  of  glass  area  as  approximate 
rules.  These  figures  should  be  considered  a  minimum. 

Empirical  rules  for  greenhouse  radiation,  quoted  by 
many  firms  dealing  in  the  apparatus,  are  usually  given  in 
the  terms  of  the  number  of  square  feet  of  glass  surface 
heated  by  one  lineal  foot  of  1%  inch  pipe.  A  very  commonly 
quoted  and  accepted  rule  is,  one  foot  of  1%  inch  pipe  to 
every  2^4  square  feet  of  glass,  for  steam;  or,  one  foot  of 
1%  inch  pipe  to  every  1%  square  feet  of  glass,  for  hot  water, 
•v\hen  the  interior  of  the  house  is  70  degrees  in  zero  weather. 
The  following  table,  from  the  Model  Boiler  Manual,  shows 
the  amount  of  surface  for  different  interior  temperatures 
and  different  temperatures  of  the  heating  medium. 

In  general,  it  may  be  said  that  in  greenhouse  heating, 
great  care  should  be  used  in  the  rating  and  the  selection 


HOT    WATER    AND    STEAM    HEATING 


of  the  boilers  or  heaters.  It  is  well  to  remember  that  the 
severe  service  demanded  by  a  sudden  change  in  the  weather 
is  much  more  difficult  to  meet  in  greenhouses  than  in  ordin- 
ary structures,  and  that  a  liberal  reserve  in  boiler  capacity 
is  highly  desirable. 

TABLE  XI. 


s« 

£§ 

0  0 

|M 

!! 

H 

400 
450 
50° 
550 
600 
(55° 
70° 
75° 
800 
85° 

Temperature  of  Water  in  Heating  Pipes 

Steam 

140° 

1600 

1800 

2000 

Three  Ibs. 
Pressure 

Square  feet  of  glass  and  its  equivalent  proportioned  to 
one  square  foot  of  surface  in  heating  pipes  or  radiator 

4.33 
8.63 
8.07 
gKfr.98 

•2.19 
1.86 
1.58 
1.37 
1.16 
.99 

5.25 
4.65 
3.92 
3-89 
2-89 
2.53 
2.19 
1.92 
1.63 
1.42 

6-66 
5-55 
4-76 
4.16 
8.63 
3.22 
2.81 
2-5 
2.17 
1.92 

7.69 
6.66 
5.71 
5. 
4.83 
3.84 
8-44 
3.07 
2.78 
2.46 

8. 
7-5 
7. 
6.5 
6. 
5.5 
5. 
4.5 
4. 
3.5 

This  table  is  computed  for  zero  weather;  for  lower 
temperatures  add  iya  per  cent,  for  each  degree  below  zero. 

81.  The  Determination  of  Pipe  Sizes: — The  theoretical 
determination  of  pipe  sizes  in  hot  water  and  steam  systems 
has  always  been  more  or  less  unsatisfactory,  first,  because 
of  the  complicated  nature  of  the  problem  when  all  points 
having  a  bearing  upon  the  subject  are  considered,  and 
second,  because  it  is  almost  an  impossibility  to  even  ap- 
proximate the  friction  offered  by  different  combinations  and 
conditions  of  piping.  The  following  rather  brief  analysis 
gives  a  theoretical  method  for  determining  pipe  sizes  where 
friction  is  not  considered. 

In  a  hot  water  system  let  the  temperatures  of  the  water 
entering  and  leaving  the  radiator  be,  respectively,  180 
and  160  degrees;  then  it  is  evident  that  one  pound  of  the 
water  in  passing  through  the  radiator,  gives  off  20  B.  t.  u. 
Under  these  conditions  the  standard  room  would  have  14000  -f- 
20  =  700  pounds  of  water  passing  through  the  radiator  per 
hour.  Converting  this  to  gallons,  it  is  found  to  be  84.03. 
But  the  radiation  for  this  room  was  found  to  be  84  square 
feet.  Whence,  it  may  be  said  that  a  hot  water  radiator 


100  ^  HEATING  AND  VENTILATION 

under  normal  conditions  of  installation  and  under  heavy 
service  requires  one  gallon  of  water  per  square  foot  of  sur- 
face per  hour.  Knowing  the  theoretical  amount  of  water 
per  hour,  it  remains  only  to  obtain  the  theoretical  speed 
at  which  it  travels,  due  to  unbalanced  columns,  to  obtain 
finally,  by  division,  the  theoretical  area  of  the  pipe. 

Consider  a  radiator  to  be  about  10  feet  above  the 
source  of  heat,  and  the  temperature  in  the  flow  riser  to  be 
180  degrees  and  in  the  return  riser  160  degrees,  good  values 
in  practice.  Now,  the  heated  water  in  the  -flow  riser 
weighs  60.5567  pounds  per  cubic  foot,  while  that  in  the 
return  riser  weighs  60.9697  pounds  per  cubic  foot.  The  mo- 

/  W  —  W   \ 
tive  force  is  f  =  g   [    )  where  g  is  the  acceleration 

\w  +  wJ 

due  to  gravity,  W  is  the  specific  gravity  (weight)  of  the 
cooler  column  and  W  is  the  specific  gravity  (weight)  of  the 
warmer  column.  Substitute  /  for  g  in  the  velocity  formula 
and  obtain  v  =  fafh  and 


/         /  W  —  W   \ 

v  =-/  2gh(   )  (36) 

\          \W  +  W      / 

Inserting  values  W,   W  and  assuming  h  =  10  feet,   we  have 


v  =  V2  X  32.2  X  10  X  .0034  =  V2-1896  =  1.47  feet  per  second. 
From  this,  it  has  become  a  custom  to  speak  of  1.5  feet  per 
second  or  5400  feet  per  hour,  as  the  theoretical  velocity  of 
water  in,  say,  a  first  floor  riser,  disregarding  the  effect  of 
all  friction  and  horizontal  connections.  Theoretical  veloci- 
ties for  any  other  height  of  column  and  for  other  temper- 
atures may  be  obtained  in  like  manner.  Continuing  this 
special  investigation  and  changing  the  84  gallons  per  hour 
to  cubic  inches  per  hour  by  multiplying  by  231,  the  internal 
pipe  area  may  be  obtained  by  dividing  by  the  unit  speed 
per  hour  which  gives  (84  X  231)  +  (5400  X  12)  =  .3  square 
inch.  This  corresponds  to  approximately  a  %  inch  pipe 
and  without  doubt,  would  supply  the  radiator  if  the  sup- 
position of  no  frictional  resistances  could  be  realized.  This 
ideal  condition,  of  course,  cannot  be  had,  nor  can  the  fric- 
tion in  the  average  house  heating  plant  be  theoretically 
treated  with  any  degree  of  satisfaction.  Hence  it  is  still 
the  custom  to  use  tables  for  the  selection  of  pipe  sizes, 


HOT    WATER    AND    STEAM    HEATING  101 

based  upon  what  experience  has  shown  to  be  good  practice. 
Such  tables,  from  various  authorities,  may  be  found  in  the 
Appendix.  It  is  safe  to  say  that  one  should  never  use  any- 
thing- smaller  than  a  1  inch  pipe  in  low  pressure  hot  water 
work. 

With  steam  systems,  where  the  heating  medium  is  a  vapor, 
and  subject  in  a  lesser  degree  to  friction,  the  discrepancy 
between  the  theoretical  and  the  practical  sizes  of  a  pipe 
is  not  so  great  as  in  hot  water.  Each  pound  of  steam,  in 
condensing,  gives  off  approximately  1154  —  181  =  973  B.  t.  u. 
To  supply  the  heat  loss  of  the  standard  room,  14000  B.  t.  u. 
per  hour,  it  would  require  14.5  pounds  of  steam  per  hour. 
When  it  is  remembered  that  the  calculated  surface  of  the 
direct  steam  radiator  for  this  room  was  56  square  feet,  it 
appears  that  a  radiator,  under  stated  conditions  and  under  a 
heavy  service,  requires  one-fourth  of  a  pound  of  steam  per  square 
foot  of  surface  per  hour.  This  may  be  shown  in  another  way: 
each  square  foot  of  steam  radiation  gives  off  255  B.  t.  u. 
per  hour;  then,  each  square  foot  will  condense  255  -j-  973  =: 
.26  +  pounds  of  steam  per  hour. 

Now  the  volume  of  the  steam  per  pound  at  the  usual 
steam  heating  pressure,  18  pounds  absolute,  is  21.17  cubic 
feet.  Since  the  standard  room  radiator  required  14.5  pounds 
per  hour,  it  would,  in  that  time,  condense  steam  corres- 
ponding to  a  void  of  21.17  X  14.5  —  307  cubic  feet  per  hour. 
This  is  the  volume  of  the  steam  required  by  the  radiator, 
and,  if  the  speed  of  the  steam  in  the  pipe  lines  be  taken 
at  15  feet  per  second,  or  54000  feet  per  hour,  the  area  of 
the  pipe  would  be  307  X  144  -7-  54000,  or  .82  square  inch, 
corresponding  very  closely  to  a  1  inch  pipe.  For  a  two- 
pipe  system  this  would  be  considered  good  practice  under 
average  conditions;  but  in  a  one-pipe  system,  where  the 
condensation  is  returned  against  the  steam  in  the  same 
pipe  that  feeds,  a  pipe  one  size  larger  would  be  taken. 

Table  33,  Appendix,  calculated  from  Unwin's  formula, 
may  be  used  in  finding  sizes  and  capacities  of  pipes  carrying 
steam.  In  addition  to  this,  Tables  26,  27,  28  and  29  give  sizes 
that  are  recommended  by  experienced  users. 

For  a  theoretical  discussion  of  loss  of  head  by  friction 
in  hot  water  and  steam  pipes,  see  Arts.  144  and  172. 

82.  Grate  Area: — To  obtain  the  grate  area  for  a  direct 
radiation  hot  water  or  steam  system  by  the  B.  t.  u.  method, 


102  HEATING  AND  VENTILATION 

the  same  analysis  as  found  in  Chapter  IV,  may  be  applied. 
The  total  B.  t.  u.  heat  loss,  H,  is  that  calculated  by  the 
formula  and  does  not  include  Hv,  the  heat  loss  due  to  ven- 
tilation, since  with  the  direct  hot  water  or  steam  system  as 
usually  installed  no  ventilation  is  provided.  In  any  special 
case  where  ventilation  is  provided  in  excess,  use  Er  instead 
of  H.  The  commercial  rating  of  heaters  and  boilers  is  a 
subject  each  day  receiving  greater  attention  at  the  hands 
of  manufacturers;  yet  it  is  a  subject  where  much  uncer- 
tainty is  felt  to  exist.  Hence  the  recommendation,  "Always 
check  grate  area  by  an  actual  calculation,"  rather  than  rely 
entirely  upon  the  catalog  ratings. 

83.  Pitch  of  Mains: — The  pitch  of  the  mains  is  quite  as 
important  in  hot  water  as  in  steam  work.     This  should  not 
be  less  than  1  inch  in  10  feet  for  hot  water  systems,  and  not 
less   than    1    inch    in    30    feet    for    steam    systems.      Greater 
pitches   than   these   are    desirable,    but    not    always    practic- 
able.    In  hot  water  plants  the  pitch  of  the  basement  mains, 
whether  flow   or  return,    is  upward   as   these   mains   extend 
from  the   source   of   heat,   that  is,   the   highest   point  is   the 
farthest  from  the  heater.     In  steam  plants  the  mains,  under 
any    condition    of    arrangement,     always     pitch     downward 
in  the  direction  of  the  flow  of  the  condensation. 

84.  Location    and    Connection    of   Radiators: — In    locat- 
ing radiators,  it  is  best  to  place  them  along  the  outside  or 
the    exposed    walls.      When    allowable,    under    the    windows 
seems   to    be    a    favorite    position.      Especially    in    buildings 
of  several  stories,  the   radiators  should  be  arranged,  where 
possible,    in    tiers,    one   vertically    above    another,    thus    re- 
ducing the  number  of  and  avoiding  the  offsets  in  the  risers. 
In  the  one-pipe  system  any  number  of  radiators  may  be  con- 
nected to  the   same   riser.     In  the   two-pipe   system   several 
radiators  may  have  either  a  common  flow  riser,  or  a  common 
return   riser,   but   should   never   have   both,   either   with   hot 
water  or  with  steam. 

The  connections  from  the  risers  to  the  radiators  should 
be  slightly  pitched  for  drainage  and  are  usually  run  along 
the  ceiling  below  the  radiator  connected.  These  connections 
should  be  at  least  two  feet  long  to  give  that  flexibility  of 
connection  to  the  radiator  made  necessary  by  the  expan- 


HOT    WATER    AND    STEAM    HEATING  103 

sion  and  contraction  of  the  long  riser.  Similarly,  all  risers 
should  be  connected  to  the  mains  in  the  basement  by  hori- 
zontals of  about  two  feet  to  allow  for  the  expansion  and 
contraction  of  the  mains.  A  system  thus  flexibly  connected 
stands  in  much  less  danger  of  developing  leaky  joints  than 
does  one  not  so  connected.  For  sizes  of  radiator  connections 
see  Table  24,  Appendix. 

85.  General  Application: — Figs.  48,  49  and  50  show  the 
typical  layout  of  a  hot  water  plant.  Due  to  the  similarity  be- 
tween hot  water  and  steam  installations,  the  former  only  will 
be  designed  complete.  In  attempting  the  layout  of  such  a 
system,  the  very  first  thing  to  be  done  is  to  decide  at  what 
points  in  the  rooms  the  radiators  should  be  placed.  This 
should  be  done  in  conjunction  with  the  owner  as  he  may 
have  particular  uses  for  certain  spaces  from  which  radia- 
tors are  hence  excluded.  The  first  actual  calculation  should 
be  the  heat  loss  from  each  room,  with  the  proper  exposure 
losses,  and  the  results  should  be  tabulated  as  the  first 
column  of  a  table  similar  to  Table  XII.  In  the 
example  here  given,  this  loss  is  the  same  as,  and  taken 
from,  the  table  of  computations  for  the  furnace  work,  Art. 
48,  the  house  plans  being  identical.  The  second  column 
of  Table  XII,  as  indicated,  is  the  square  feet  of  radiation; 
and  since  this  is  a  hot  water,  direct  radiation  system,  it 
is  obtained  by  taking  .006  of  the  items  in  the  first  column 
according  to  formula  30.  Knowing  this,  a  type  and 
height  of  radiator  can  be  selected,  and  the  number  of 
sections  determined  by  Table  X.  Next  obtain  the  lengths 
of  radiators  by  multiplying  the  number  of  sections  by  the 
total  thickness  of  the  sections,  as  given  in  Table  X,  and 
determine  whether  or  not  the  radiator  of  such  a  length 
will  fit  into  the  chosen  space.  If  not,  then  a  radiator  of 
greater  height  and  larger  surface  per  section  must  be 
selected.  Riser  sizes  and  connections  may  be  taken  ac- 
cording to  Tables  26  and  24  respectively.  The  column  of 
Table  XII  headed  "Radiators  Installed"  gives  first  the  num- 
ber of  sections;  second,  the  height  in  inches;  and  third,  the 
number  of  columns  or  type  of  the  section. 

Locate  radiators  on  the  second  floor  and  transfer  the 
location  of  their  riser  positions  to  first  floor  plan,  then  to 
the  basement  plan.  Locate  radiators  on  the  first  floor  and 


104  HEATING  AND    VENTILATION 

transfer  their  riser  locations  to  the  basement  plan,  which 
will  then  show,  by  small  circles,  the  points  at  which  all 
risers  start  upward.  This  arrangement  will  aid  greatly  in 
the  planning  of  the  basement  mains. 

The  keynotes  in  the  layout  of  the  basement  mains 
should  be  simplicity  and  directness.  If  the  riser  positions 
show  approximately  an  even  distribution  all  around  the 
basement,  it  may  be  advisable  to  run  the  mains  in 
complete  circuits  around  the  basement.  If,  again,  the 
riser  positions  show  aggregation  at  two  or  three  localities, 
then  two  or  three  mains  running  directly  to  these  localities 
would  be  most  desirable.  As  an  example,  take  the  applica- 
tion shown  here.  The  basement  plan  shows  three  clusters 
of  riser  ends,  one  under  the  kitchen,  another  under  the 
study,  and  a  third  on  the  west  side  of  the  house.  This 
condition  immediately  suggests  three  principal  mains,  as 
shown.  The  main  toward  the  kitchen  supplies  the  bath, 
chamber  4  and  the  kitchen,  making  a  total  of  131  square 
feet.  Being  only  about  13  feet  long,  it  would  readily  carry 
this  radiation  if  of  2  inch  diameter.  See  Table  29.  The 
main  to  the  study  and  the  hall  supplies  chamber  1,  the  hall 
and  the  study,  making  a  total  of  221  square  feet,  which 
can  be  carried  by  a  2%  inch  pipe.  The  main  to  the  west  side 
of  the  house  supplies  chamber  2,  chamber  3,  the  sitting  room 
and  the  dining  room,  a  total  of  249  square  feet,  which  would 
almost  require  a  3  inch  main,  according  to  the  table,  were 
it  not  for  its  comparatively  short  length.  A  2^  inch  pipe 
would  amply  supply  this  condition. 

In  hot  water  work,  as  well  as  in  steam,  it  is  customary 
to  take  the  connections  to  flow  risers  from  the  top  of  the 
mains,  thus  aiding  the  natural  circulation,  Fig.  31.  If  not 
taken  directly  from  the  top  of  the  main,  it  is  often  taken  at 
about  45  degrees  from  the  top.  This  arrangement,  with  a 
short  nipple,  a  45  degree  elbow,  and  the  horizontal  connec- 
tion about  1%  to  2  feet  long,  makes  a  joint  of  sufficient 
flexibility  between  the  main  and  riser  to  avoid  expansion 
troubles. 

In  the  selection  of  a  heater  or  boiler  much  that  has 
been  said  concerning  furnaces  applies.  The  heater  or  boiler 
should,  above  all,  have  ample  grate  area,  checked  on  a  B. 
t.  u.  basis,  and  should  have  a  sufficient  heating  surface  so 


HOT    WATER    AND    STEAM    HEATING 


105 


designed  that  the  heated  gases  from  the  fire  impinge  per- 
pendicularly upon  it  as  often  as  may  be  without  seriously 
reducing  the  draft.  As  shown  by  the  total  of  the  radiation 
column,  a  hot  water  boiler  should  be  selected  of  such  rated 
mains  and  risers.  Since  this  loss  is  usually  taken  from 
20  to  30  per  cent.,  depending  upon  the  thoroughness  with 
which  the  basement  mains  are  insulated,  the  heater  for  this 
house  should  have  a  rated  capacity  of  not  less  than  720 
square  feet  of  radiation. 

TABLE  XII. 


| 

1* 

Radiators 
installed 

Lengths 
ofRad'or 
installed 

Riser 
Sizes 

II 

o"S 

*-«  *-* 

g 

"0 

•d 

°§ 

tsS 

°\\ 

1 

g 

1 

is 

s 

il 

hS  ° 

& 

£ 

3 

* 

S 

o 

"S3 

*a 

ffii: 

& 

£ 

o 

£ 

^ 

c 

rt 

Sitting  R  

14000 

84 

15-82-3 

14-44-3 

34 

42 

1* 

i^ 

1« 

Dining  R. 

10800 

65 

14-26-3 

18-26-3 

32 

54 

1% 

1J4 

IK 

Study 

13250 

80 

82-14-3 

20-14-P 

72 

60 

1V4 

1% 

Kitchen  

11900 

70 

12-82-3 

8  -45-4 

24 

1H 

1H 

l>i 

Rec'p'n  Hall  

14000 

84 

15-82-3 

14-44-8 

84 

42 

i^ 

1V4 

Chamber  1  

9400 

57 

18-26-3 

16-26-3 

30 

48 

iM 

IK 

IX 

Chamber  2 

9850 

60 

13-26-3 

16-26-3 

30 

48 

1% 

1M 

IX 

Chambers  

6600 

40 

10-26-3 

12-26-3 

23 

36 

i 

1 

1 

Chamber  4  

5600 

35 

10-26-3 

12-26-8 

28 

36 

i 

1 

1 

Bath... 

4400 

6-26-3 

7-26-3 

14 

21 

j 

1 

j 

"I  — 

leoi 

166 


HEATING  AND  VENTILATION. 


4«Lr 

*JL_t          ttfia-Zft- 


I  ---       L,  15'    9i"  -  ifjl^'j.  -  9'  -  Sir 

-  ----  **  —  ^ 


J 


PLAM 

Ceiling  6 ' 

Fig.   48. 


HOT    WATER    AND     STEAM    HEATING  107 


fipoR.  PLAN  — 
Ceiling  /O ' 

Fig.   49. 


108 


HEATING  AND  VENTILATION 


•5ttohD  riPOR.  PLAN 

Ceiling  $' 

,    Fig.    60. 


HOT    WATER    AND    STEAM    HEATING  109 

86.  Insulating:  Steam  Pipes: — In  all  heating  systems, 
pipes  carrying  steam  or  water  should  be  insulated  to  protect 
from  heat  losses,  unless  these  pipes  are  to  serve  as  radiating 
surfaces.  In  a  large  number  of  plants  the  heat  lost  through 
these  unprotected  surfaces,  if  saved,  would  soon  pay  for 
first  class  insulation.  The  heat  transmitted  to  still  air 
through  one  square  foot  of  the  average  wrought  iron  pipe 
is  from  2  to  2.2  B.  t.  u.  per  degree  difference  of  temperature 
between  the  inside  and  the  outside  of  the  pipe.  Assuming 
the  minimum  value,  and  also  that  the  pipe  is  fairly  well 
protected  from  air  currents,  the  heat  loss  is,  with  steam  at 
100  pounds  gage  and  80  degrees  temperature  of  the  air, 
(338  —  80)  X  2  =  516  B.  t.  u.  per  hour.  With  steam  at  50, 
25,  and  10  pounds  gage  respectively  this  will  be  436,  374  and 
320  B.  t.  u.  If  the  pipe  were  located  in  moving  air,  this  loss 
would  be  much  increased.  It  is  safe  to  say  that  the  average 
low  pressure  steam  pipe,  when  unprotected,  will  lose  be- 
tween 350  and  400  B.  t.  u.  per  hour.  Taking  the  average  of 
these  two  values  and  applying  it  to  a  six  inch  pipe  100  feet 
in  length,  for  a  period  of  240  days  at  20  hours  a  day,  we  have 
a  heat  loss  of  171  X  375  X  240  X  20  =  307800000  B.  t.  u.  With 
coal  at  13000  B.  t.  u.  per  pound  and  a  furnace  efficiency  of  60 
per  cent,  this  will  be  equivalent  to  39461  pounds  of  coal, 
which  at  $2.00  per  ton  will  amount  to  $39.46.  From  tests 
that  have  been  run  on  the  best  grades  of  pipe  insulation,  it  is 
shown  that  80  to  85  per  cent,  of  this  heat  loss  could  be 
saved.  Taking  the  lower  value  we  would  have  a  financial 
saving  of  $31.56  where  the  covering  is  used.  Now  if  a  good 
grade  of  pipe  covering,  installed  on  the  pipe,  is  worth  $35.00, 
the  saving  in  one  year's  time  would  nearly  pay  for  the 
covering. 

To  be  effective,  insulation  should  be  porous  but  should 
be  protected  from  air  circulation.  Small  voids  filled  with 
still  air  make  the  best  insulating  material.  Hence,  hair 
felt,  mineral  wool,  eiderdown  and  other  loosely  woven  ma- 
terials are  very  efficient.  Some  of  these  materials,  however, 
disintegrate  after  a  time  and  fall  to  the  bottom  of  the  pipe, 
leaving  the  upper  part  of  the  pipe  comparatively  free.  Many 
patented  coverings  have  good  insulating  qualities  as  well  as 
permanency.  Most  patented  coverings  are  one  inch  in  thick- 
ness and  may  or  may  not  fit  closely  to  the  pipe.  A  good  ar- 


110 


HEATING  AND  VENTILATION 


rangement  is  to  select  a  covering  one  size  larger  than  the 
pipe  and  set  this  off  from  the  pipe  by  spacer  rings.  This 
air  space  between  the  pipe  and  the  patented  covering  is  a 
good  insulator  in  itself.  Table  35,  Appendix,  gives  the 
results  of  a  series  of  experiments  on  pipe  covering,  obtained 
at  Cornell  University  under  the  direction  of  Professor  Car- 
penter. These  values  are  probably  as  nearly  standard  as 
may  be  had. 

87.  "Water  Hammer: — When  steam  is  admitted  to  a  cold 
pipe,  or  to  a  pipe  that  is  full  of  water,  it  is  suddenly  con- 
densed and  causes  a  sharp  cracking  noise,  that  under  certain 
conditions  may  become  so  severe  as  to  crack  the  fittings  and 
open  up  the  joints.  The  noise  is  produced  by  the  sudden  rush 
of  water  in  an  endeavor  to  fill  the  vacuum  produced  by  the 
condensed   steam.      Steam  at   atmospheric   pressure   occupies 
1644  times  the  volume  of  the  water  that  produced  it,  hence, 
by    suddenly    condensing    it,    a    very    high    vacuum    may    be 
produced.     This  action  causes  a  relatively  high  velocity  in 
any  body  of  water  adjacent  to  it.     The   worst  condition   is 
found   when  a   quantity   of   steam   enters   a  pipe   filled  with 
water.       Condensation    suddenly    takes    place    and    the    two 
bodies   of  water  come   together  with   high   velocity   causing 
severe   concussion.     Steam  should  always   be  admitted  to  a 
cold  pipe,  or  to  one  filled  with  water,  very  slowly. 

88.  Returning    the    Water    of    Condensation,    in    a    Low 
Pressure     Steam     Heating     System,    to     the     Boiler: — In     re- 


Eig.  51.  Fig.    52. 

turning  the  water  of  condensation  to  the  boiler  four  methods 
are  in  use;  gravity,  steam  traps,  steam  loops  and  steam 
pumps.  The  gravity  system  is  the  simplest  and  is  used  in  all 
cases  where  the  radiation  is  above  the  level  of  the  boiler  and 


HOT    WATER    AND    STEAM    HEATING  111 

where  the  boiler  pressure  is  used  in  the  mains.  In  a  gravity 
return,  no  special  valves  or  httings  are  necessary,  but  a  free 
path  with  the  least  amount  of  friction  in  it  is  provided  be- 
tween the  radiators  and  a  point  on  the  boiler  below  the  water 
line.  No  traps  of  any  kind  should  be  placed  in  this  return 
circuit. 

When  the  radiation  is  below  the  water  line,  or  where  the 
pressure  in  the  mains  is  less  than  that  in  the  boiler,  some 
form  of  steam-trap  must  be  put  in  with  special  provision  for 
returning  this  water  to  the  boiler.  Two  kinds  of  traps  may 
be  had,  low  pressure  and  high  pressure.  The  first  is  well 
represented  by  the  bucket  trap,  Fig.  51,  and  the  second,  by 
the  Bundy  trap,  Fig.  52.  The  action  of  these  traps  is  as 
follows:  Bucket  trap. — Water  enters  at  D  and  collects 
around  the  bucket,  which  is  buoyed  up  against  the  valve. 
The  water  collects  and  overflows  the  bucket  until  the  com- 
bined weight  of  the  water  and  bucket  overbalances  the 
buoyancy  of  the  water.  The  bucket  then  drops  and  the 
steam  pressure  upon  the  inside,  acting  upon  the  surface  of 
the  water,  forces  it  out  through  the  valve  and  central  stem 
to  the  outlet  B.  When  a  certain  amount  of  this  water  has 
been  ejected,  the  bucket  again  rises  and  closes  the  valve. 
This  action  is  continuous.  Bundy  trap. — Water  enters  at  D 
through  the  central  stem  and  collects  in  the  bowl  A,  which 
is  held  in  its  upper  position  by  a  balanced  weight.  When 
the  water  collects  in  the  bowl  sufficiently  to  lift  the  weight, 
the  bowl  drops,  the  valve  E  opens,  and  steam  is  admitted 
to  the  bowl,  thus  forcing  the  water  out  through  the  curved 
pipe  and  the  valve  E.  This  action  is  continuous. 

Each  trap  is  capable  of  lifting  the  water  approximately 
2.4  feet  for  each  pound  of  differential  pressure.  Thus,  for  a 
pressure  of  5  pounds  gage  within  the  boiler  and  2  pounds 
gage  on  the  return,  the  water  may  be  lifted  7  feet  above 
the  trap,  or  say,  to  the  top  of  an  ordinary  boiler.  This  is  not 
sufficient,  however,  to  admit  the  water  into  the  boiler 
against  the  pressure  of  the  steam.  A  receiver  should  be 
placed  here  to  catch  the  water  from  the  separating  trap 
and  deliver  it  to  a  second  trap  above  the  boiler  which,  in 
turn,  feeds  the  boiler.  Live  steam  is  piped  from  the  boiler 
to  each  trap,  but  the  steam  supply  to  the  lower  trap  is 


112 


HEATING  AND  VENTILATION 


throttled,  to  give  only  enough 
pressure  to  lift  the  water 
into  the  receiver.  A  system 
connected  up  in  this  way  is 
shown  in  Fig.  53.  Traps 
which  receive  the  water  of 
condensation  for  the  pur- 
pose of  feeding  the  boiler 
are  called  return  traps  and 
sometimes  work  under  a 
higher  pressure'  of  steam 
than  the  separating  traps. 
Many  different  kinds  of  traps 
are  in  general  use  but  these 
will  illustrate  the  principle 
of  returning  the  condensation 
to  the  boiler. 

A  very  simple  arrangement,  and  yet  a  very  difficult  one 
to  operate  satisfactorily,  is  by  the  use  of  the  steam  loop,  Fig. 
54.  The  water  of  condensation  from  the  radiators  drains 
to  the  receiver  A,  which  is  in  direct  communication  with  the 
riser  B.  The  drop  leg  D,  being  in  communication  with  the 
boiler  through  a  check  valve  which  opens  toward  the  boiler 
at  the  lowest  point,  is  filled  with  water  to  the  point  X,  suffi- 
ciently high  above  the  water  line  of  the  boiler  that  the 
static  head  balances  the  differential  pressure  between  the 
steam  in  the  boiler  and  that  in  the  condenser.  The  horizon- 
tal run  of  pipe  C  serves  as  a  condenser  and,  in  producing  a 
partial  vacuum,  lifts  the  water  from  the  receiver.  This 
water  is  not  lifted  as  a  solid  body,  but  as  slugs  of  water 
interspersed  with  quantities  of  steam  and  vapor.  The  water 
in  A  is  at  or  near  the  boiling  point  and  the  reduced  pressure 
in  B  reevaporates  a  portion  of  it  which,  in  rising  as  a 
vapor,  assists  in  carrying  the  rest  of  the  water  over  the 
goose-neck.  When  the  condensation  in  D  rises  above  the 
point  X,  the  static  pressure  overbalances  the  differential 
steam  pressure,  and  water  is  fed  to  the  boiler  through  the 
check. 

To  find  the  location  of  the  point  X,  above  the  water  line 
in  the  boiler,  the  following  will  illustrate:  Let  the  pres- 
sures in  the  boiler,  condenser  and  receiver  be  respectively 


HOT     WATER    AND    STEAM    HEATING 


113 


5,  2  and  4  pounds  gage,  then  the  differential  pressure  between 
the  boiler  and  condenser  is  3  pounds  per  square  inch.  If  the 
weight  of  one  cubic  foot  of  water  at  212  degrees  is  59.76 
pounds,  then  the  pressure  is  .42  pounds  per  square  inch  for 
each  foot  in  height.  Stated  in  other  words,  one  pound  dif- 
ferential pressure  will  sustain  2.4  feet  of  water.  With  a 
pressure  difference  of  3  pounds,,  this  gives  3  -r-  .42  =  7.2 
feet  from  the  water  level  in  the  boiler  to  the  point  X,  not 
taking  into  account  the  friction  of  the  piping  and  check 
which  would  vary  from  10  to  30  per  cent.  Assuming  this 
friction  to  be  20  per  cent,  we  have,  7.2  -^  .80  =  9  feet  of  head 
to  produce  motion  of  the  water. 


Fig.  54. 

The  length  of  the  riser  pipe  B  and  its  diameter,  depend 
upon  the  differential  pressure  between  the  condenser  and 
the  receiver,  and  upon  the  rapidity  of  condensation  in  the 
horizontal. 

With  a  differential  pressure  of  2  pounds  this  would  sus- 
pend 2X2.4  =  4.8  feet  of  solid  water.  The  specific  gravity, 
however,  of  the  mixture  in  this  pipe  is  much  less  than  that 
of  solid  water.  For  the  sake  of  argument  let  this  specific 


114  HEATING  AND  VENTILATION 

gravity  be  20  per  cent,  of  that  of  solid  water,  then  we  would 
have  a  possible  lift,  not  including  friction,  of  5  X  4.8  =  24 
feet.  This  is  24  —  9  =  15  feet  below  the  water  level  in  the 
boiler.  The  diameter  of  the  riser  may  vary  for  different 
plants,  but  for  any  given  plant  the  range  of  diameters  is 
very  limited.  These,  as  has  been  stated,  are  usually  found 
by  experiment. 

A  drain  cock  should  be  placed  in  the  receiver  at  the 
lowest  point.  When  cold  water  has  collected  in  the  re- 
ceiver it  is  necessary  to  drain  this  water  to  the  sewer  before 
the  loop  will  work.  An  air  valve  should  be  placed  at  the  top 
of  the  goose-neck  to  draw  off  the  air.  If  the  horizontal  pipe 
is  filled  with  air,  there  will  be  no  condensation  and  the  loop 
will  refuse  to  work.  Never  connect  a  steam  loop  to  a  boiler 
in  connection  with  a  pump  or  any  other  boiler  feeder.  To 
determine  whether  a  loop  is  working  or  not,  place  the  hand 
on  the  horizontal'  pipe.  If  this  is  cold  it  is  not  working. 

The  last  method  mentioned  for  feeding  condensation  to 
the  boiler  was  by  the  use  of  a  steam  pump.  This  is  fully  dis- 
cussed in  Art.  161. 

89.  Suggestions  for  Operating  Hot  Water  Heaters  and 
Steam  Boilers: — Before  firing  up  in  the  morning,  examine 
the  pressure  gage  to  see  if  the  system  is  full  of  water.  If 
there  be  any  doubt,  inspect  the  water  level  in  the  expan- 
sion tank.  If  it  is  a  steam  system,  examine  the  gage  glass 
and  try  the  cocks  to  see  if  there  is  sufficient  water  in  the 
boiler. 

See  that  all  valves  on  the  water  lines  are  open.  On  the 
steam  system  try  the  safety  valve  to  see  if  it  is  loose  and 
see  if  the  pressure  gage  stands  at  zero. 

Clean  the  fire  and  sprinkle  over  it  a  small  amount  of 
fresh  coal. 

Open  up  the  drafts  and  when  the  fire  is  burning  well 
fill  up  with  coal. 

In  starting  a  fire  under  a  cold  boiler  it  should  not  be 
forced,  but  should  warm  up  gradually. 

Hard  coal  may  be  thrown  evenly  over  the  fire.  Soft  coal 
should  be  banked  in  front  on  the  grate,  until  the  gases  are 
driven  off.  It  is  then  distributed  back  over  the  fire. 

The  thickness  of  the  fire  will  vary  from  four  inches  to 
one  foot  depending  upon  the  draft  and  the  kind  of  coal. 


HOT    WATER    AND    STEAM    HEATING  115 

Clean  the  fire  when  it  has  burned  low,  partially  closing 
the  drafts  while  cleaning:. 

In  a  boiler  or  heater,  using  the  water  over  continuously, 
there  will  be  little  need  of  cleaning  out  the  inside.  In  a 
system  using  fresh  water  continuously,  however,  the  boiler 
should  be  blown  off  and  cleaned  about  once  or  twice  a  month. 
Never  blow  off  a  boiler  while  hot  or  under  heavy  pressure. 

In  every  system  the  heater  or  boiler  should  be  thoroughly 
overhauled  and  cleaned  before  firing  up  in  the  fall. 

Keep  the  ash  pit  clean  and  protect  the  grates  from  burn- 
ing out. 

Keep  the  tubes  and  gas  passages  clean  and  free  from  soot. 

Inspect  the  pressure  gage,  glass  gage,  water  cocks  and 
thermometers  frequently. 

In  case  of  low  water  in  a  steam  system,  cover  the  fire 
with  wet  ashes  or  coal  and  close  all  the  drafts.  Do  not 
open  the  safety  valve.  Do  not  feed  water  to  the  boiler.  Do 
not  draw  the  fire.  Keep  the  conditions  such  as  to  avoid  any 
sudden  shock.  After  the  steam  pressure  has  dropped,  draw 
the  fire. 

Excessive  pressure  may  be  caused  by  the  sticking  of  the 
•safety  valve  in  the  steam  system,  or  by  the  stoppage  of  the 
water  line  to  the  expansion  tank  in  the  hot  water  system. 
The  safety  valve  should  never  be  allowed  to  lime  up,  and  the 
expansion  tank  should  always  be  open  to  the  heater  and  to 
the  overflow. 

When  leaving  the  fires  for  the  night,  push  them  to  the 
rear  of  the  grate  and  bank  them  as  stated  in  Art.  59. 


References  on  Hot  Water  and  Steam. 

TECHNICAL  BOOKS. 

Snow,  Principles  of  Heat.,  Chap.  IX,  X,  I.  C.  S.,  Prin.  of  Heat, 
and  Vent.  p.  1185,  1091.  Monroe,  Steam  Heat.  &  Vent.,  p.  13.  Law- 
ler,  Hot  Water  Heating,  p.  19.  Carpenter,  Heat.  &  Vent.  Bldgs.,  p. 
150,  231.  Thompson,  House  Heat,  ty  (steam  &  Water,  p.  15.  Hubbard 
Power,  Heat.  &  Vent.,  pages  433,  464,  484,  505,  510. 
TECHNICAL  PERIODICALS. 

Engineering  News.  Suggestions  for  Ehx'st  Steam  Heat,  Apr. 
7,  1904,  p.  332.  An  Improved  Steam  Heat.  System,  Thermo- 
grade  System,  July  23,  1903,  p.  80.  Factory  System  of  the 
United  Shoe  Machinery  Co.,  W.  C.  Snow,  May  25,  1905,  p.  537. 
Heating  a  Trolley  Car  Barn,  J.  I.  Brewer,  April  29,  1909,  p. 
462.  Engineering  Review.  Heat.  &  Vent,  of  the  new  Parental 
Home  and  School  at  Flushing,  L.  L,  Jan.  1910,  p.  48.  A  Hot 
Water  System  with  Radiators  and  Boiler  on  the  same  Level, 
J.  P.  Lisk,  Aug.  1908,  p.  34.  A  Hot  Water  Heat.  System  for 
a  City  Residence,  J.  P.  LLsk,  June  1909,  p.  44.  Hot  Water 
Heat.  Apparatus  in  Plymouth  Church,  Brooklyn,  N.  Y.,  Dec. 
1908,  p.  19.  Heat.,  Vent,  and  Temperature  Regulation  in  the 


116  HEATING  AND  VENTILATION 


Measles  Pavilion  of  the  Kingston  Ave.  Hospital,  Brooklyn, 
N.  Y.,  Jan.  1910,  p.  35.  Heat,  and  Vent.  Plant  of  the  Boston 
Safe  Deposit  and  Trust  Company's  Building,  C.  L.  Hubbard, 
April  1910,  p.  37.  Heat,  and  Vent.  Installation  in  the  Burnet 
St.  School,  Newark,  N.  J.,  Jan.  1909,  p.  20.  A  Unique  Low 
Pressure  Steam  Heat.  Apparatus,  Feb.  1909,  p.  38.  Practical 
Points  on  Steam  Heating  (Direct  Heating),  C.  L.  Hubbard, 
Aug.  1908,  p.  29.  (Indirect  Heat.),  Sept.  1908,  p.  19.  (Exhaust 
Steam  Heat.),  Nov.  1908,  p.  21.  Steam  Heating  Systems,  Wm.  J. 
Baldwin,  March  1905,  p.  7.  Machinery.  Shop  Heating  by  Direct 
Radiation,  C.  L.  Hubbard,  July  1910,  p.  884.  Sizes  of  Pipe  Mains 
for  Hot  Water  Heating,  C.  L.  Hubbard,  Sept.  1909,  p.  38. 
The  Railway  Review.  Heating  System  of  the  Scranton  St.  Rail- 
way Shops,  June  13,  1908,  p.  480.  Heating  of  Passenger  Trains 
May  23,  1908,  p.  408.  The  Pennsylvania  R.  R.  System  of  Heat, 
and  Vent.  Passenger  Trains,  Feb.  22,  1908,  p.  157.  Vent,  and 
Heating  of  Coaches  and  Sleeping  Cars,  July  18,  1908,  p.  586. 
Hot  Water  Heating  Arrangements  for  Passenger  Stations,  Oct. 
10,  1908,  p.  829.  Typical  Heating  Plants,  Horace  L.  Winslow 
Co.,  June  18,  1910,  p.  596.  The  Heating  &  Ventilating  Magazine.  Res- 
idence Heating  by  Direct  and  Indirect  Hot  Water,  July,  1905, 
p.  25.  Carrying  Capacities  of  Pipes  in  Low  Pressure  Steam 
Heating,  Wm.  Kent,  E  eb.  1907,  p.  7.  Standard  Sizes  of  Steam 
Pipes,  Jas.  A.  Donnelly,  Jan.  1907,  p.  21.  Formula  for  Pipe 
Sizes  in  Hot  Water  Heating,  Oliver  H.  Schlemmer,  Sept.  1907, 
p.  9.  Co-efficient  of  Transmission  in  Cast  Iron  Radiation, 
John  R.  Allen,  Aug.  1908,  p.  19.  Relative  Capacities  of  Pipes, 
John  Jaeger,  May  1907,  p.  1.  Methods  of  Figuring  Radiation, 
Gerard  W.  Stanton,  Dec.  1907.  Computation  of  Radiating  Sur- 
face, J.  Byers  Holbrook,  Nov.  1904,  p.  77.  Domestic  Engineering  . 
A  Practical  Manual  of  Steam  and  Water  Heating.  E.  R.  Pierce, 
CSeries  of  Articles),  Vol.  51,  No.  2,  April  9,  1910;  Vol.  53,  No. 
9,  Nov.  26,  1910.  Proportions  and  Power  of  Low  Pressure 
Heating  Boilers,  Vol.  47,  No.  11,  June  12,  1909,  p.  319.  How  to 
Install  and  Cover  a  Steam  or  Hot  Water  Main,  "Phoenix,"  Vol. 
46,  No.  10,  March  6,  1909,  p.  278.  How  to  Secure  Correct  Pipe 
Sizes  for  Low  Pressure  Steam  Heating,  E.  K.  Munroe,  Vol.  45, 
No.  9,  Nov.  28,  1908,  p.  243.  Rules  for  Proportioning  Indirect 
Heating  Plants,  R.  T.  Crane,  Vol.  49,  No.  6,  Nov.  6,  1909,  p. 
143.  Trans.  A.  #.  H.  &  V.  E.  Circulation  of  Hot  Water,  J.  S. 
Brennan,  Vol.  XI,  p.  93.  Residence  Heating  by  Direct  and 
Indirect  Hot  Water,  E.  F.  Capron,  Vol.  XI,  p.  174.  Standard 
Sizes  of  Steam  Mains,  J.  A.  Donnelly,  Vol.  XIII,  p.  43.  The 
Carrying  Capacity  of  Pipes  in  Low  Pressure  Steam  Heating, 
Wm.  Kent,  Vol.  XIII,  p.  54.  Heating  and  Ventilating  a  Group 
of  Public  Schools,  S.  R.  Lewis,  Vol.  XIII,  p.  187.  The  Com- 
bined Pressure  and  Vacuum  Systems  of  Steam  Heating,  G. 
Hoffman,  Vol.  XIII,  p.  223.  Sizes  of  Return  Pipes  in  Steam 
Heating  Apparatus,  J.  A.  Donnelly,  Vol.  XII,  p.  109.  Pro- 
portioning Hot  Water  Radiation  in  Combination  Systems  of 
Hot  Water  and  Hot  Air  Heating,  R.  C.  Carpenter,  Vol.  VII, 
p.  132.  Tests  of  Radiators  with  Superheated  Steam,  R.  C. 
Carpenter,  Vol.  VII,  p.  185.  Relative  Economy  of  Steam, 
Vapor,  Vacuum  and  Hot  Water  Heating  for  Residences,  Vol. 
XII,  p.  341.  The  Relation  between  the  Completeness  of  Air 
Removal  and  the  Efficiency  of  Steam  Radiators,  Vol.  XII, 
p.  315.  Advantage  of  Low  Pressure  Hot  Water  Heating  Sys- 
tems, Vol.  XI,  p.  183,  209.  Measurements  of  Wall  Radiators, 
Vol.  XII,  p.  361.  Advantages  of  Standard  Dimensions  of 
Radiator  Valves  and  Connections,  Vol.  XIII,  p.  148.  The 
Relative  Healthfulness  of  Direct  and  Indirect  Heating  Sys- 
tems, Vol.  XIII,  p.  36.  Improving  the  Heating  Capacity  of  a 
Radiator  by  an  Electric  Fan,  Vol.  VIII,  p.  222. 


CHAPTER   IX. 


MECHANICAL,  WARM  AIR  HEATING  AND 
VENTILATING    SYSTEMS. 


DESCRIPTION  OF  SYSTEMS  AND  APPARATUS  EMPLOYED. 

90.  Fire-places,  Stoves,  Furnaces  and  Direct  Radiation 
Systems    of    both    steam   and   hot    water   have,    individually, 
advantages    and    disadvantages,    but,    in    common,    all    lack 
what   is   increasingly  being   considered  as   of  more   import- 
ance   than    heating,    namely,    positive    ventilation.     Merely    to 
heat  a  poorly  ventilated  apartment  only  serves  to  increase 
the    discomfort    of    the    occupants,    and    modern    legislative 
bodies  are  reflecting  the  opinion  of  the  times  by  the  passage 
of    compulsory    ventilation    laws    affecting    buildings    with 
numerous    occupants,    such    as    factories,    barracks,    school 
houses,   hotels   and  auditoriums.     To  meet   this  demand   for 
the  positive   ventilation   of  such   classes   of  buildings,   there 
has  been  developed  what  is  variously  known  as  the  hot  Mast 
heating  system,  plenum  system,  fan  Wast  system   or  mechanical  warm 
air  system. 

91.  Elements    of   the    Mechanical    Warm   Air    System: — 

Known  by  whatever  name,  this  system  contemplates  the 
use  of  three  distinctly  vital  elements;  first,  some  form  of 
hot  metallic  surface  over  which  the  forced  air  may  pass 
and  be  heated;  second,  a  blower  or  fan  of  some  description 
to  propel  the  air;  and  third,  a  proper  arrangement  of  ducts 
or  passageways  to  distribute  this  heated  air  to  desired 
locations.  P  igs.  66  and  67  show  these  essentials,  fan, 
heating  coils  and  ducts  in  their  relative  positions  with  con- 
nections as  found  in  a  typical  plant  of  this  system.  Many 
attachments  and  improved  mechanisms  may  be  had  to-day 
in  connection  with  this  system,  such  as  air  washers  and 
humidifiers,  automatic  damper  control  systems,  and  brine 
cooling  systems  whereby  the  heating  coils  may  be  used 
as  cooling  coils,  and,  during  hot  weather,  be  made  to 
maintain  the  temperature  within  the  building  from  10  de- 


118 


HEATING   AND   VENTILATION 


grees  to  15  degrees  lower  than  the  atmosphere.  Any  of 
these  auxiliaries,  however,  change  in  no  way  the  necessity 
for  the  three  fundamentals  named  and  their  general  ar- 
rangement as  shown. 

92.  Variations  in  the  Design  ~f  Mechanical  Warm  Air 
Systems: — With  regard  to  the  position  of  the  fan,  two 
methods  of  installing  the  system  are  common.  The  first 
and  most  used  is  that  snown  by  Fig.  (55),  a,  where  the  fan 
Is  in  the  basement  of  the  building  and  forces  the  air  by 
pressure  upward  through  the  ducts  and  into  the  rooms. 
This  causes  the  air  within  the  entire  building  to  be  at  a 


!  / 


Fig. 


Diagram  of  Plenum 
System. 


b. 


Diagram  of  Exhaust 
System. 


pressure  very  slightly  higher  than  the  atmosphere,  and 
hence  all  leakages  will  be  outward  through  doors  and  win- 
dow crevices.  A  system  so  instaPed  is  usually  called  a 
plenum  system.  The  fan  may,  however,  be  of  the  exhausting 
type,  Fig.  (55),  b,  and  placed  in  the  attic  with  which  ducts 
from  the  rooms  connect,  so  that  the  fan  tends  to  keep  the 
air  of  the  building  at  a  slight  vacuum  as  compared  with 
the  atmosphere,  thus  inducing  ventilation.  Air  is  then 


PLENUM   WARM   ATR   HEATING 


119 


supposed  to  enter  the  basement  inlet,  pass  over  the  coil 
surface,  and,  when  heated,  pass  to  the  various  rooms 
through  the  ducts  provided.  But  air  from  the  atmosphere 
will  just  as  readily  leak  in  at  windows  or  other  crevices, 
as  to  come  in  over  the  heaters,  and  then  the  system  will 
fail  in  its  heating  work.  B  or  this  reason  the  exhaust  heating 
system,  as  it  is  usually  known,  is  seldom  installed,  except 
where  aid  in  the  prompt  removal  of  malodors  is  desired. 
Combined  plenum  and  exhaust  systems  are  to  be  recom- 
mended wherever  the  expense  can  be  justified. 

93.  Blowers  and  Fans: — Many  methods  of  moving  air 
for  ventilating  and  heating  purposes  have  been  devised, 
some  positive  at  all  times,  others  so  dependent  upon  the  ex- 
istence of  certain  conditions  as  to  be  a  constant  source  of 
trouble.  It  is  coming  to  be  a  very  generally  accepted  fact, 
that  if  air  is  to  be  delivered  at  definite  times,  in  definite 
quantities  and  in  definite  places,  it  must  be  force^.  there,  and 
not  merely  allowed  to  go  under  conditions  readily  changing 
or  disappearing.  The  recognition  of  this  fact  has  led  to  a 
very  common  use  of  the  mechanical  fan  or  blower  for  im- 
pelling air,  and  this  use  has,  in  turn,  caused  the  develop- 
ment of  fans  and  blowers  to  a  fairly  high  degree  of 
efficiency. 


120 


HEATING  AND  VENTILATION 


By  the  aid  of  the  mechanical  apparatus,  air  may  be 
moved  positively  in  either  of  two  ways,  by  the  exhaust  method 
and  by  the  plenum  method,  each  having  developed  fans  best 
suited  to  its  needs.  In  the  exhaust  method  the  fan  is  corn- 


Fig.  57. 

monly  of  the  disk  or  propellor  blade  type,  shown  in  Fig.  56  or 
57,  is  usually  installed  in  the  attic  or  near  the  top  of  the 
building,  although  with  a  system  of  return  ducts  it  may 
be  installed  in  the  basement,  and  moves  the  air  by  suction. 
Tue  plenum  system  uses  a  fan  of  the  paddle  wheel  type, 
shown  in  Bigs.  58  and  59;  the  first  is  the  standard  form 
of  fan  wheel  in  common  use,  and  the  second  is  a  more 
recent  development  of  the  same,  called  the  "turbine"  fan 
wheel,  shown  direct  connected  to  a  De  Laval  steam  turbine. 
Tne  wheels  of  the  fans  are  also  shown.  Tests  of  the  latter 
wheel  seem  to  show  a  somewhat  higher  efficiency  than  has 
heretofore  been  possible  with  the  older  forms.  Both  of 
these  forms  of  fans  are  used  in  plenum  work,  and  are 
placed  on  the  forcing  side  of  the  circulating  system  just 
between  the  air  Intake  and  the  heater  coils,  or  just  follow- 
ing the  heater  coils,  and  hence  produce  a  pressure  within 
the  building  or  suite  heated,  so  that  leakages  are  outward 
and  not  so  detrimental  to  the  good  working  of  the  plant 
as  in  the  exhaust  system. 


PLENUM   WARM  AIR   HEATING 


121 


The  motive  power  for  fans  may  be  of  four  kinds, 
electric  direct  drive,  steam  engine  or  steam  turbine  direct 
drive,  and  belt  and  pulley  drive,  as  shown  in  Figs.  57,  58,  59 


Fig".  58. 


Fig.  59. 


and  60.  Which  of  these  drives  will  be  the  most  appropriate 
will  depend  entirely  upon  local  conditions  and  the  nature 
of  the  available  power  supply.  The  steam  engine  or  steam 
turbine  drive  is  perhaps  the  most  common,  since  some 
steam  must  be  present  for  the  supply  of  the  heating  coils, 
and  since,  too,  the  exhaust  of  the  engine  or  turbine  may 
be  used  to  supplement  the  live  steam  used  for  heating. 
See  Art.  114. 

Pan  housings  are  made  in  many  different  styles,  and  of 
various  materials,  the  more  readily  to  fit  any  given  set  of 
conditions.  Materials  employed  may  be  of  brick,  wood,  sheet 
steel  or  combinations  of  these.  Steel  housings  are  the  most 
common  and  are  made  in  such  a  variety  of  patterns  as 
will  fit  any  requirement  of  plenum  duct  direction.  What 
are  known  as  full  housings  are  those  where  the  entire  fan 
wheel  is  encased  with  steel  and  the  entire  unit  is  self-con- 


122  HEATING  AND  VENTILATION 


tained  and  above  the  floor  line.  Three-quarter  housings  are 
those  where  only  the  upper  three-fourths  of  the  fan  wheel 
is  encased,  the  completion  of  the  air-sweep  around  the 
paddles  being  obtained  by  properly  forming  the  brick  foun- 
dation upon  which  the  fan  is  installed.  The  larger  fans 
are  commonly  three-quarter  housed,  especially  if  they  are 
to  deliver  air  directly  into  underground  ducts.  Fig.  58 
shows  a  full  housing  and  Fig.  60  a  three-quarter  housing. 
The  circular  opening  in  the  housing  around  the  shaft 
of  the  wheel  is  the  inlet  of  the  fan,  the  air  being  thrown 
by  centrifugal  force  to  the  periphery  and  at  the  same 
time  given  a  circular  motion,  thus  leaving  the  fan  tan- 
gentially  through  the  discharge  opening.  This  discharge 
may  be  had  delivering  at  any  angle  around  the  wheel,  and 
fans  may  be  had  with  two  or  more  discharge  openings,  usu- 


PLENUM   WARM   AIR   HEATING 


123 


ally  referred  to  as  "multiple  discharge  fans,"  as  shown  in 
Fig.  61. 


Fig.    61. 

94.      Fresh   Air   Entrance   to   Building:   and   to    Rooms: — 

The  air  may  enter  through  the  building  wall  at  the  ground 
level  or  it  may  be  taken  from  a  stack  built  for  the  pur- 
pose, providing  a  down  draft  with  entrance  for  the  air 
at  the  top.  This  may  be  done  in  case  rio  washing  or  clean- 
ing systems  are  applied  and  in  case  the  air  carries  a  great 
deal  of  dust  or  dirt  in  from  the  street  or  from  other 
similar  places.  Usually  in  isolated  plants  or  in  small  cities, 
the  air  is  taken  in  near  the  ground  level  from  some  area- 
way  that  is  fairly  free  from  dust.  In  the  larger  cities, 
however,  either  a  washing  system  is  installed  to  cleanse 
the  air  before  it  is  sent  around  to  the  rooms,  or  the  air 
is  taken  from  an  elevation  somewhat  above  the  ground 
as  spoken  of  before.  The  velocity  of  the  air  should  be  from 
700  to  1000  feet  per  minute  at  this  point  and  where  grill 
work  or  shutters  of  any  sort  are  put  in  the  opening,  they 
are  usually  so  planned  as  not  to  obstruct  the  flow  of  the 
air  seriously.  Usually  a  plain  flat  wire  screen  is  placed 


124 


HEATING  AND  VENTILATION 


in  the  opening  to  keep  out  leaves,  and  doors  are  swung 
from  the  inside  in  such  a  way  as  to  be  thrown  open,  leaving 
practically  the  full  value  of  the  opening  as  a  net  area. 

Air  entrance  to  rooms  is  accomplished  through  reg- 
isters or  gratings  which  cover  the  ends  of  rectangular  ducts 
or  conduits  called  stacks,  built  into  the  brick  walls  and  open- 
ing Into  the  respective  rooms  much  as  shown  in  section  by 
Fig.  20.  Register  sizes  considered  standard  are  given  in 
Table  14,  Appendix.  The  velocity  of  the  air  at  a  plenum 
register  may  be  somewhat  higher  than  with  a  simple  fur- 
nace, installation.  With  the  plenum  system  the  heat  reg- 
isters are  usually  placed  well  above  the  heads  of  the  occu- 
pants, near  the  ceiling,  and  the  vent  registers  usually  near 
the  floor.  Velocities  allowable  at  registers  and  up  stacks 
are  shown  in  Table  XIII,  page  136. 

95.  Plenum  Heating:  Surfaces: — Heating  surfaces  as 
used  to-day  in  connection  with  plenum  systems  may  be 
divided  into  two  classes:  coil  surface,  made  of  loops  of  1  or 
1%  inch  wrought  iron  pipe  and  cast  surface,  made  of  hollow 
rectangular  castings  provided  with  numerous  staggered  pro- 
jections to  increase  the  outside  surface  and  provide  greater 
air  contact.  To  make  a  neater  of  either  kind  of  surface, 
successive  units  are  placed  side  by  side,  until  the  requisite 
'total  area  and  depth  has  been  obtained.  See  Arts.  110 
and  111. 

Coil  surface  is  of 
three  kinds,  that  hav- 
ing the  pipes  inserted 
vertically  into  a  hori- 
zontal cast  iron  header 
which  forms  the  base  of 
the  section,  Fig.  62,  that 
having  the  pipes  hori- 
zontally between  two 
vertical  side  headers, 
Fig.  63,  and  that  having 
one  header  vertical  and 
one  header  horizontal 
called  the  mitre  coil,  Fig. 
64.  The  first  and  last 
forms  shown  are  made 
Fig.  62.  with  two,  three  or  four 


PLENUM   WARM   AIR   HEATING 


125 


pipes  in  depth.  The  standard  number  of  pipes  in  any  one 
section  is  four.  Sometimes  these  pipes  are  spaced  in  straight 
lines  parallel  with  the  wind  and  sometimes  are  staggered. 
Staggered  spacing  no  doubt  makes  each  pipe  slightly  more  ef- 
ficient but  it  adds  friction  to  the  fan.  Efficiency  tests  of  both 
spacings.  however,  show  little  difference  in  these  methods. 
The  horizontal  sections  and  the  mitre  sections  present  this  ad- 
vantage over  the  vertical  pipe  sections,  that  the  steam  and 
condensation  is  always  flowing  in  the  same  direction  and 


JHg.    63. 


=) 


drainage  is  very  simple.  With 
the  vertical  pipe  section, 
steam  in  one  half  of  the  pipes 
must  pass  upward  against  the 
di  ection  of  the  flow  of  con- 
densation or  it  must  carry  the 
condensation  with  it.  That 
half  of  the  header  supplying 
pipes  which  carry  steam  up- 
ward is  usually  drained  for 
condensation  by  a  small  hole 
directly*  into  the  return  with 
the  result  that  steam  often 
blows  through  the  header 


Fig.  64. 


126 


HEATING  AND  VENTILATION 


without  traversing  the  pipe 
circuits.  The  third,  or  mitre 
section,  in  addition  to  per- 
fect drainage,  has  perfect  ex- 
pansion; the  vertical  header 
serving  as  a  steam  supply, 
and  the  horizontal  header  as 
a  drain,  permit  every  pipe 
to  assume  any  position  nec- 
essary to  account  for  a  rea- 
sonable change  of  length. 

Cast   iron   radiating   surface 
for  plenum  systems   is   shown 
in    Fig.    65.      It    is    composed, 
primarily,    of   sections    not    un- 
like   the    sections    of   an   ordi- 
nary   direct    radiator    in    the 
way  in  which  they  are  joined 
together  at   the   top  and  bot- 
tom by  nipples,   thus   forming 
what  is  termed  a  stack.  Stacks 
are    again    assembled,    one    in 
front  of  another,  with  respect 
to  the   direction   in  which  the 
air   passes   through   them,    the 
completed    heater    being    then 
more   or   less   cubical    in  pro- 
portion.     The    figure   shows   a  ^_  Condensation' 
heater   two   sections   in   depth  Fig.  65. 
and  ten  sections  in  width.     Provided  the  conditions  demand 
it,    the    heater   may    be   built   two    or    even   three   stacks    in 
height,  thus  doubling  or  tripling  the  gross  wind  area.     See 
Art.  111. 

Sections  are  usually  made  in  but  one  thickness,  9  inches, 
and  in  three  heights,  40  inches,  50  inches  and  60  inches,  pre- 
senting respectively,  11.5,  14  and  17  square  feet  of  surface. 
It  is  unusual  to  assemble  less  than  five  or  more  than  twenty- 
five  sections  to  the  stack.  By  the  proper  adjustment  of  num- 
ber of  sections  to  the  stack,  and  of  stacks  to  the  heater, 
any  requirement  of  hot  blast  work  may  be  met. 


PLENUM    WARM   AIR   HEATING 


127 


ELEVATION. 

Fig.  66.  Fan  Room  Layout  with  Single  Ducts  along 
Basement  Ceiling  and  all  Mixing  Dampers  at  Plenum 
Chamber. 


12S 


HEATING  AND  VENTILATION 


Pig.    67.     E  an   Room  Layout   with   Double  Underground 
Ducts  and  Mixing  Dampers  at  Base  of  Room  Stacks. 


PLENUM   WARM   AIR   HEATING  129 

No  matter  what  kind  or  type  of  heater  may  be  selected, 
certain  methods  of  installing-  them  have  become  common. 
They  may  be  placed  on  either  the  suction  or  the  force  side 
of  the  fan,  usually  the  former  in  drying-  or  evaporating- 
plants,  but  more  often  the  latter  in  heating-  plants.  Because 
of  their  weight,  ample  and  firm  foundations  must  be  pro- 
vided. In  most  installations  for  heating-  purposes,  where 
both  tempered  and  heated  air  is  supplied,  the  heater  should 
be  raised  on  its  foundation  18  to  24  inches  to  allow  a 
damper  and  passage  way  for  tempered  air. 

96.  Division    of    Coil    Surface: — It    is    considered    best 
practice   to  install  a  hot  blast  heater  in  two   parts,   known 
as  the  tempering  coil  and  the  heating  coil.       In  the  calculations. 
Arts.  107-111,  the  total  heating  surf ace- $s  first  obtained  and 
then  this  is  split  up  into  whatever  arrangement   is   desired. 
The  tempering  coils  should  be  placed  in  the  air  passageway, 
just  within  the   intake  for  the  building,  and  should  contain 
from   one-fourth   to    one-third  of   the  total   heating-   surface. 
In  this  way  the  air  is  tempered  before  it  reaches  any  other 
apparatus,  thus  protecting  from  accumulation  of  frost  on  fan 
and  bearings  and  aiding  in  the  process  of  lubrication.     The 
.main   heat    coil   is   placed   just   beyond   the   fan   on   its   force 
side.      Exhaust    steam    from    the    engine    is    most    commonly 
used  in  the  tempering  coil  only,  and  live  steam  of  properly 
reduced  pressure  in   the   main  heater.     This   may   be   varied 
by  conditions,  however,  and  all  surface  supplied  by  exhaust 
steam  if  it  is  thought  advisable. 

97.  Single  Duct  Plenum   System: — Duct   systems   in  hot 
blast    work   may   be   either   of    the    single    duct   type    or   the 
double  duct  type.      In  the  single  duct  plant,   every  horizontal 
duct  is  carried  independently  from  the  base   of  the  room  to 
be  heated  to  the  small  room  called  the  plenum  chamber,  which 
receives    the    hot   blast   from   the    heater.      This    chamber   is 
divided  into  an  upper  and  a  lower  part,  the  upper  receiving 
the    heated    air   that    has    been    forced    through    the    heater, 
while  the  lower  part  receives  only  air  that  has  been  through 
the    tempering    coils.      The    leader    duct,    from    the    base    of 
each  vertical   room-duct,   is   led  directly   opposite  the  parti- 
tion between  these  two  chambers,  and  a  damper,    regulated 
by  some  system  of  automatic  control  from  the  rooms  to  be 
heated,   governs  whether  cool  air  from  the   lower  chamber, 
or  hot  air   from  the   upper  chamber,   or  a  mixture   of  both, 


130 


HEATING  AND  VENTILATION 


shall  be  sent  to  the  rooms.  It  can  be  readily  seen  that  this 
system  produces  rather  a  complicated  net  work  of  dampers 
and  ducts  at  the  plenum  chamber  and  this  disadvantage  has 
limited  its  use  very  much. 

98.  Double  Duct  Plenum  Systems: — As  its  name  indi- 
cates, this  system  runs  a  double  leader  duct  from  the 
plenum  chamber  to  the  base  of  each  vertical  room-duct, 
the  upper  one  of  these  ducts  being  in  direct  communication 
with  the  upper  part  of  the  .plenum  chamber  and  carries 

hot  air,  while  the  lower 
one  is  in  communication 
with  the  lower  part  of 
the  plenum  chamber  and 
carries  cool  air.  No  mix- 
ing- or  throttling  is  done 
except  at  the  base  of  the 
vertical  room-duct,  where 
the  mixing  damper  is  lo- 
cated, it  being  controlled 
by  hand  or  by  automatics 
directly  from  the  room 
above.  With  this  scheme 
it  is  evident  that  the 
leader  ducts  for  each 
room  need  not  be  run 
singly,  but  all  the  ducts 
having  the  same  general 
direction  combined  in 
one  large  double  trunk, 
from  which  branches  are 
taken  to  the  various 
room-ducts  as  required. 

Fig.   68.  The      difference     between 

the  two  systems  is  shown  by  the  two  sketches,  Figs. 
66  and  67. 

A  hot  blast  plant  may  be  installed  as  a  basement  or  as 
a  sub-basement  system.  If  the  former,  the  leaders  will  be 
suspended  from  the  basement  ceiling  and  constructed,  usu- 
ally, of  sheet  metal,  thus  forming  what  is  often  called  a 
"false  ceiling."  If  the  latter,  they  will  be  just  below  the 
floor  of  the  basement  and  will  be  constructed  of  brick  and 
mortar,  or  of  concrete,  about  four  inches  thick.  For  designs 


PLENUM   WARM   AIR   HEATING 


131 


of  conduits,  ducts  and  dampers,  see  Figs.  60,  66,  67  and 
68,  the  last  showing  a  simple  and  direct  installation  often 
applied  to  factories  of  several  stories.  Fig.  69  shows  a 
complete  steel  housed  plenum  unit  of  fan,  coils,  dampers, 
and  duct  connections. 


Fig.    69. 


99.  Air  Washing  and  Humidifying  Systems: — In  con- 
nection with  mechanical  warm  air  heating  and  ventilating 
systems,  there  is  often  installed  apparatus  for  washing 
and  humidifying  the  air.  In  crowded  city  districts  where 
the  air  is  laden  with  dust,  soot,  th.e  products  of  combus- 
tion and  other  harmful  gases,  its  purification  and  moisten- 
ing becomes  a  most  important  problem.  The  plenum  system 
of  heating  and  ventilating  lends  itself  most  readily  to 
the  solution  of  this  problem,  with  the  result  that  modern 
practice  is  tending  more  each  day  toward  the  combined 
installation  of  ventilating  and  humidifying  apparatus.  Fig. 
70  shows  a  plenum  system  augmented  by  an  air  washing, 
purifying  and  humidifying  apparatus. 

A  purifier  usually  contemplates  the  installation  of  two 
parts,  a  washer  and  an  eliminator.  The  washer  consists  essen- 
tially of  an  air  duct,  usually  located  immediately  behind 
the  tempering  coils,  and  provided  with  streams  or  sprays  of 
water  through  which  the  air  must  pass.  Numerous  schemes 
for  breaking  up  the  water  in  the  finest  sprays  are  on  the 
market,  and  their  relative  merits  may  be  judged  from  trade 
literature.  Having  caught  the  dust  particles  and  dissolved 
the  soluble  gases  from  the  air,  the  water  falls  to  a  collecting 
pan  at  the  bottom  of  the  spray  chamber,  and  from  there 
is  again  pumped  through  the  spraying  nozzles.  As  the 
water  becomes  too  dirty  or  too  warm,  a  fresh  supply  is 


132  HEATING  AND  VENTILATION 

delivered  to  the  collecting-  pan.  A  small  independent  cen- 
trifugal pump  is  commonly  used  for  the  circulation  of 
the  spray  water. 


Fig.   70. 

After  passing  through  the  washer,  the  air  next  encoun- 
ters the  eliminator,  the  purpose  of  which  is  to  remove  or 
eliminate  the  surplus  moisture  and  water  particles  remain- 
ing suspended  in  the  air.  This  is  accomplished  by  an 
arrangement  of  more  or  less  complicated  baffle  plates,  which 
cause  the  air  to  change  its  direction  suddenly  many  times 
in  succession,  with  the  effect  that  the  water  particles  im- 
pinge upon  and  adhere  to,  the  baffle  plates.  These  are  suit- 
ably drained  to  the  collecting-  pan  beneath  the  washer. 
As  the  air  leaves  the  eliminator  and  enters  the  fan  it  may 
be  relieved,  with  good  apparatus,  of  98  per  cent,  of  all  dust 
and  dirt,  may  be  supplied  with  moisture  to  very  near  the 
saturation  point,  and,  in  summer  time  under  favorable  con- 
ditions, may  be  cooled  from  5  to  10  degrees  lower  than  the 
atmosphere.  This  is  due  to  the  cooling  effect  of  vaporizing 
part  of  the  water. 

Special  air  cooling  plants  have  been  installed  in  connec- 
tion with  the  plenum  system  of  ventilation,  whereby  refrig- 
erated brine  could  be  circulated  in  the  regular  heating  coils. 
The  description  of  such  a  plant  with  data,  may  be  found  in 
the  transactions  of  the  A.  S.  H.  &  V.  E.  for  the  year  1908. 


CHAPTER   X. 


MECHANICAL,  WARM  AIR  HEATING  AND 
VENTILATING  SYSTEM. 


AIR,    HEATING   SURFACE    AND    STEAM    REQUIREMENT. 
PRINCIPLES  OF  THE  DESIGN. 

100.  Definitions  of  Terms: — In  the  work  under  this  gen- 
eral heading,   some   of  the  technical  abbreviations   that  are 
frequently  used  are   the  following:     H  =  B.   t.   u.  heat  loss 
per  hour  by  the  formula,  Hv  =  B.  t.  u.  heat  loss  per  hour  by 
ventilation,    H'   =  total    B.    t.    u.    loss    including    ventilation 
loss,  Q  =  cubic  feet  of  air  used  per  hour  as  a  heat  carrier, 
Qf  =  cubic  feet  of  air  used  including  extra  air  for  ventila- 
tion,  R  =  total   square   feet   of   heating   surface    in    indirect 
heaters,    ts    =    temperature    of    the    steam    or    water    in   the 
heaters,  t  =  highest  temperature  of  the  air  at  the   register 
(let  this   be   the   same   as   the   temperature   of  the   air   upon 
leaving  the  heater),  t'  =  temperature  of  the  air  in  the  room, 
tv  =  temperature   of  the  air  at  the  register  when  extra  air 
is  used  for  ventilation,  to  =  temperature  of  the  outside  air, 
K  =  rate  of  transmission  of  heat  per  square  foot  of  surface 
per  degree  difference  per  hour,  N  =  the  number  of  persons 
to    be   provided    with   ventilation,    V  =  velocity    in   feet   per 
minute   and  v  =  velocity  in   feet  per  second.     Other  abbre- 
viations are  explained  in  the  text. 

101.  Theoretical    Considerations: — For   illustrative    pur- 
poses,   references   will    frequently   be   made   throughout   this 
discussion   to   a  sample  plenum   design,   Figs.   74,   75   and   76. 
These  show  the  essential  points   of  most  plenum   work  and 
will   serve  as  a  basis  for  the  applications.     In  working  up 
any   complete  design  the    following   points   should   be  theo- 
retically considered  for  each  room:     the  heat  loss,  the  cubic 
feet  of  air  per  hour  needed  as  a  heat  carrier    (this   should 
be   checked    for   ventilation),   .the    net   area   of   the    register 
in   square   inches,   the   catalog   size   of  the   register,   and  the 
area  and  size  of  the  ducts.     In  addition  to  these  the  follow- 
ing  should   be    investigated    for   the    entire   plant:    the    size 
of  the  main  leader  at  the  plenum  chamber,   the  size   of  the 
principal    leader  branches,   the   square   feet   of  heating   sur- 
face in  the  coils,  the  lineal  feet  of  coils,  the  arrangements 
of  the   coils    in   groups   and   sections,    the    horse  power   and 


134  HEATING  AND  VENTILATION 

the  revolutions  per  minute  of  the  fan  including  the  sizes 
of  the  inlet  and  the  outlet  of  the  fan,  the  horse  power 
of  the  engine  including  the  diameter  and  the  length  of 
stroke,  and  the  pounds  of  steam  condensed  per  hour  in  the 
coils. 

Fresh  air  is  taken  into  the  building  at  the  assumed 
lowest  temperature,  to  degrees,  is  carried  over  heated  coils 
and  raised  to  t  degrees,  is  propelled  by  fans  through  ducts 
to  the  rooms  and  then  exhausted  through  vent  ducts  to 
the  outside  air,  thus  completing  the  cycle.  It  will  be  the 
object  to  so  discuss  this  cycle  that  it  will  be  general  and 
so  it  will  apply  to  any  case  which  may  be  brought  up. 

102.  Heat  Loss  and  Cubic  Feet  of  Air  Exhausted  per 
Hour: — It  is  assumed  here,  that  in  all  mechanical  draft 
heating  and  ventilating  systems,  tlie  circulating  air  is  all  taken 
from  tlie  outside  and  thrown  away  after  being  used.  Some  installa- 
tions have  arrangements  for  returning  the  room  air  to  the 
coils,  for  reheating,  but  such  schemes  should  be  considered 
as  features  added  to  the  regular  design  rather  than  as 
being  a  necessary  part  of  it.  It  is  best  to  design  the  plant 
with  the  understanding  that  all  the  air  is  to  be  thrown 
away,  then  it  will  be  large  enough  for  any  service  that  it 
is  expected  to  handle.  Having  found  H  by  some  acceptable 
formula,  the  total  heat  loss  is  (compare  with  Arts.  29  and 
36.) 

(Q    or  Q')    (f  —  to) 

H'  =  H  -\ (40) 

55 

When  *'  =   70   and   to  =  zero,   this   formula   reduces  to 
H'  =  H  +  1.27    (Q     or  Q') 

To  determine  whether  Qo  or  Qf  will  be  used  find  how  many 
people  would  be  provided  with  ventilating  air  with  the 
volume  Q.  If  Q  =  55  H  -j-  (t  —  *'),  *  =  140  and  f  =  70,  then 

55  H  H  H 

N  = = =  approximately (41) 

1800  (t—  O  2290  2300 

If  more  people  than  N  will  be  using  the  room  at  any  one 
time,  then  Q'  will  be  used  instead  and  this  value  would  be 
1800  times  the  number  of  persons  in  the  room.  In  any 
ordinary  case,  Q  will  be  sufficient.  When  this  is  so,  formula 
(40)  reduces  to 

H'  =    2   H  (42) 


PLENUM   WARM   AIR   HEATING  135 

The  reasoning-  of  this  formula  is  easily  seen  when  it  is  re- 
membered that  the  heat  given  off  from  the  air  in  dropping 
from  the  register  temperature,  140°,  to  the  room  tempera- 
ture, 70%  goes  to  the  radiation  and  leakage  losses,  H,  while 
that  given  off  from  the  inside  temperature,  70°,  to  that  of 
the  outside  temperature,  0°,  is  charged  up  to  ventilation 
losses,  Hv.  Since,  then,  these  values  are  equal,  H'  =  H  -j-  H» 
=  2  H. 

APPLICATION. — Referring  to  Fig.  75,  room  15,  and  Table 
XXVI,  page  140,  it  is  seen  that  the  calculated  heat  loss  H,  for 
this  room,  with  f  =  70  and  to  =  0,  is  70224  B.  t.  u.  per  hour; 
also,  that  the  cubic  feet  of  air,  Q,  if  t  =  140,  is  54775  per 
hour.  Applying  formula  (42),  the  total  heat  loss,  H',  be- 
comes 140448  B.  t.  u.  per  hour,  or  twice  the  amount  found 
by  the  heat  loss  formula.  With  54775  cubic  feet  of  air  sent 
to  the  room  per  hour,  this  will  provide  good  ventilation  for 
thirty  persons.  Suppose,  however,  that  fifty  persons  were 
to  be  provided  for;  this  would  require  50  X  1800  —  90000 
cubic  feet  of  air  per  hour.  With  this  increased  number  of 
people  in  the  room,  the  total  heat  loss  would  not  be  as 
stated  above,  but  would  be  according  to  formula  (40) 

90000-  (70  —  0) 

B'  =  70224  H —  184864. 

55 

103.     Temperature  of  the  Entering  Air  at  the  Register: 

— In  plenum  work,  the  registers  are  placed  higher  in  the 
wall  and  the  velocity  of  the  air  is  usually  carried  a  little 
higher  than  in  furnace  work.  It  may  be  said  that  140°  is 
probably  the  accepted  temperature  for  design,  excepting 
where  an  extra  amount  of  air  is  demanded  for  ventilation 
purposes.  In  the  latter  case,  the  temperature  of  the  air 
would  necessarily  drop  below  140°  in  order  that  the  room 
would  not  be  overheated.  The  general  formula  is 

55  H 
tv  =  t'   +  —  (43) 

APPLICATION. — Referring  to  room  15  and  (compare  with 
Art.  38)  assuming  the  heat  loss  to  have  been  figured  as 
before  with  ventilating  air  supplied  sufficient  for  50  per- 
sons, 90000  cubic  feet  per  hour,  then  the  temperature  of 
the  air  at  the  register  is 

55  H 

t  =  70  H =  103%* 

90000 


136 


HEATING  AND  VENTILATION 


The  temperature  of  the  air  at  the  register  is  the 
same  or  slightly  less  than  the  temperature  of  the  air  upon 
leaving  the  coils.  If  this  room  were  to  be  the  only  one 
heated,  then  the  coils  would  be  figured  for  a  final  temper- 
ature of  the  air  at  104°,  but  other  rooms  may  have  air 
entering  at  higher  temperatures,  hence  the  temperature  t 
upon  leaving  the  coils  should  be  that  of  the  highest  t  at 
the  registers. 

104.  Cubic  Feet  of  Air  needed  per  Hour: — The  following 
amount    of   air   will    be    needed   per   hour   as   a   heat   carrier 
(compare  with  Art.  36). 

55   H  H 

Q  = ;  where  t  =  140  and  V  —  70,  Q  —  

*  —  t'  1.27 

If  extra   air  be   needed  for  ventilation,   Q'  =   1800   N. 

105.  Air    Velocities,    V,    in   the    Plenum    System: — Table 
XIII  gives  the  velocities  in  feet  per  minute  that  have  been 
found   to   give  good  satisfaction   in   connection   with   blower 
systems. 

TABLE  XIII. 
Air  Velocities  in  the  Plenum  System. 


Fresh 
Aii- 
Intake 

Over 
Coils 

Main 
Duct 
Near 
Fan 

Smaller 
Branch 
Ducts 

Stacks 

Registrs 
or  other 
Open'gs 

Offices, 
Schools,  etc. 

s  ? 

S> 

800  to  1200  F.  P.  M. 
Average  KXK)  F.  P.  M. 

1200  to 
1800 
say  1500 

800  to 
1200 
say  900 

500  to 
700 
say  600 

300  to 
400 
say  300 

Auditoriums, 
Ohurches.etc. 

1500  to 
2000 
say  1800 

1000  to 
1500 
say  1200 

600  to 
800 
say  700 

400  to 
600 
say  400 

Shops  and 
Factories. 

1500  to 
3000 
say  2000 

1000  to 
2000 
say  1500 

600  to 
1000 
say  800 

400  to 

800 
say  500 

106.      Cross    Sectional    Area    of    Registers,    Ducts,    etc: — 

With  the  above  velocities  in  feet  per  minute,  the  square 
inches  of  net  opening  at  any  part  of  the  circulating  sys- 
tem can  be  obtained  by  direct  substitution  in  the  general 
formula. 

144  (0  or  Q') 

A  =  (Q  or  Q')  X  =  2.4  (44) 

60  V  V 


PLENUM   WARM   AIR   HEATING  137 

The  calculated  duct  sizes,  of  course,  refer  to  the  warm 
air  duct.  The  cold  air  duct  in  double  duct  systems  need  not 
be  so  large  because  on  warm  days,  when  only  tempered  air 
is  needed,  the  steam  may  be  turned  off  from  one  or  more 
of  the  heaters  and  the  warm  air  duct  can  then  be  used  to 
furnish  what  otherwise  would  be  required  from  the  cold 
air  duct.  On  account  of  this  flexibility,  it  seems  only  nec- 
essary to  make  the  cold  air  duct  about  one-half  the  cross 
sectional  area  of  the  warm  air  duct.  For  convenience  of 
installation,  therefore,  it  would  be  well  to  make  the  form- 
er of  equal  width  to  the  latter  and  one-half  as  deep,  unless 
by  so  doing  the  cold  air  duct  becomes  too  shallow. 

APPLICATION. — Assuming  2000000  cubic  feet  of  air  to  pass 
through  the  main  heat  duct,  5  ig.  74,  per  hour  at  the  velocity 
of  1800  feet  per  minute,  the  duct  will  be  approximately  20 
square  feet  in  cross  section,  or  2y2  by  8  feet.  The  two  main 
branches  at  B,  will  carry  about  800000  cubic  feet  per  hour 
each  at  the  same  velocity  and  will  be  7.4  square  feet  in 
area  or,  say,  2  by  4  feet.  The  same  branches  at  C,  will 
carry  about  400000  cubic  feet  per  hour  each  at  a  velocity  of 
1500  feet  per  minute  and  will  be  4.4  square  feet  in  area  or, 
say,  2  by  2%  feet  and  the  branch  D,  will  carry  about  300000 
cubic  feet  at  a  velocity  of  1200  feet  per  minute  and  will  be, 
say,  1^2  by  2%  feet. 

The  stack  sizes  were  first  figured  for  the  velocity  of  600 
feet  per  minute.  These  sizes  were  then  made  to  fit  the  lay- 
ing of  the  brick  work  such  that  the  velocities  would  be 
anywhere  between  300  to  600  feet  per  minute.  The  net 
register  was  figured  for  an  air  velocity  of  300  feet  per 
minute  and  the  gross  registers  were  assumed  to  be  1.6 
times  the  net  area.  See  Art.  126. 

107.      Square  Feet  of  Heating:  Surface,  R,  in  the  Coils: — 

To  determine  theoretically  the  number  of  square  feet  of 
heating  surface  in  the  coils  of  an  indirect  heater,  the  fol- 
lowing formula  may  be  used, 

H' 
R  =  (45) 

E(t...l^l 


\  2 

Since  the  coils  are  figured  from  the  entire  building  loss, 
Hr  will  include  the  sum  of  all  the  heat  losses  of  the  various 
rooms.  The  chief  concern  in  the  use  of  this  formula,  as 


138  HEATING  AND  VENTILATION 

stated,  is  to  determine  the  best  value  for  K,  the  rate  of 
transmission.  Prof.  Carpenter  in  H.  and  V.  B.,  Art.  52, 
quotes  extensively  from  experiments  with  coils  in  blower 
systems  of  heating  and  summarizes  all  in  the  formula,  K  = 
2  +  1.3  V^T  where  v  =  average  velocity  of  air  over  the  coils 
in  feet  per  second.  With  the  four  velocities  most  appli- 
cable to  this  part  of  the  work,  i.  e.,  800,  1000,  1200  and  1500 
feet  per  minute,  this  becomes 

800    feet   per  minute  K  =  6.9 

1000    feet    per  minute  K  —  7.3 

1200    feet    per  minute  K  —  7.8 

1500    feet    per  minute  K  —  8.5 

In  the  table  of  probable  efficiencies  of  indirect  radiators  in 
Art.  54  by  the  same  author,  the  values  are  somewhat  high- 
er, being, 

750   feet  per   minute   K  =     7.1 

1050   feet  per   minute   K  =     8.35 

1200   feet  per   minute  K  =     9. 

1500    feet  per  minute   K  =  10. 

The  values  of  K,  as  given  here,  are  certainly  very  safe 
when  compared  to  quotations  from  other  experimenters, 
some  of  them  exceeding  these  values  by  50  per  cent.  It 
is  always  well  to  remember  that  a  coil  that  has  been  in 
service  for  some  time  is  less  efficient  than  a  new  coil,  be- 
cause of  the  dirt  and  oil  deposits  upon  the  surface,  hence 
it  is  best  in  designing,  not  to  take  extreme  values  for  ef- 
ficiency. Assuming  K  =  8.5  and  1000  feet  per  minute  air 
velocity,  which  are  probably  the  best  values  to  use  in  the 
calculations,  also  t»  =  227  (5  pounds  gage  pressure),  t  — 
140  and  to  =  0,  formula  45  becomes 

Er  H'  H' 

R  =  —  say  (46) 

/               140 +  0\      1335  1400 

8.5/227 } 

Table  XIV  quoted  by  Mr.  C.  L.  Hubbard  in  Power  Heat- 
ing &  Ventilation,  Part  III,  page  557,  gives  the  efficiencies 
of  forced  blast  pipe  heaters  and  the  temperatures  of  air 
delivered. 


PLENUM   WARM   AIR   HEATING 


139 


TABLE  XIV. 

Efficiencies  of  Forced-Blast  Pipe  Heaters,  and  Temperatures 

of    Air    Delivered. 
Velocity   of   air   over   coils   at   800    feet   per   minute. 


Rows 
of  Pipe 
Deep 

Tetnp.  to  which  the  air 
will  be  raised  from  zero 

Efficiency  of  the  heating  sur- 
face in  B.t.u.per  sq.ft.  perhr 

Steam  pressure  in  heater 

Steam  pressure  in  heater 

5  Ib. 

20  Ib. 

60  Ib. 

5  Ib. 

20  Ib. 

60  Ib. 

4 

30 

35 

45 

1600 

1800 

2000 

6 

50 

55 

65 

1600 

1800 

2000 

8 

65 

70 

85 

1500 

1650 

1850 

10 

80 

90 

105 

1500 

1650 

1850 

12 

95 

105 

125 

1500 

1650 

1850 

14 

105 

120 

140 

1400 

1500 

1700 

16 

120 

130 

150 

1400 

1500 

1700 

18 

130 

140 

160 

1300 

1400 

1600 

20 

140 

150 

170 

1300 

1400 

1600 

For  a  velocity  of  1000  feet  per  minute  multiply  the 
temperatures  given  in  the  table  by  0.9  and  the  efficiencies 
by  1.1. 

Mr.  F.  R.  Still  of  the  American  Blower  Co.,  Detroit, 
gives  the  following  formula  for  the  total  B.  t.  u.  trans- 
mitted per  square  foot  of  surface  per  hour  between  the 
temperature  of  the  steam  and  that  of  the  entering  air. 

Total  B.  t.   u.   transmitted  =  c  ^v^ts  —  fo)  (47) 

in  which  case  v  is  the  velocity  in  feet  per  second  and  c  is 
a  constant  as  follows: 


140 


HEATING  AND  VENTILATION 


TABLE  XV. 
Values   of   c. 


Safe  Factor 

Max.  Factor 

1  section     4  rows  of  pipe 

8.45 

4.4 

2  sections    8  rows  of  pipe 

3. 

8-4 

3  sections  12  rows  of  pipe 

2-63 

2.85 

4  sections  16  rows  of  pipe 

2.88 

2.45 

5  sections  20  rows  of  pipe 

2.12 

2.2 

6  sections  24  rows  of  pipe 

1.95 

2.05 

7  sections  28  rows  of  pipe 

1.80 

1.95 

8  sections  82  rows  of  pipe 

1.65 

1.85 

9  sections  86  rows  of  pipe 

1.52 

1.8 

10  sections  40  rows  of  pipe 

1-4 

1.75 

From  the  above  values  of  c,  Table  XVI  has  been  com- 
piled, assuming  *s  =  227,  to  —  0  and  c  =  a  safe  value. 

TABLE  XVI. 


•31 


Total  transmission  in  B.  t.  u.  per  sq.  ft.  per  hour. 
*     =  227;  *     =  °« 


«•  <D 

|! 

Bows  of  pipe  deep. 

ii 

>s 

4 

8 

12 

16 

20 

24 

28 

82 

800 

2840 

2470 

2164 

1920 

1750 

1606 

1450 

1860 

1000 

8200 

2790 

2440 

2170 

1900 

1810 

1670 

1535 

1200 

8500 

8040 

2670 

2860 

2150 

1980 

1825 

1678 

1500 

8950 

8400 

2981 

2645 

2400 

2220 

2020 

1870 

Cast  iron  heaters  are  being  used  for  indirect  heating  in 
many  cases,  replacing  the  old-fashioned  pipe  coil  heaters. 
The  efficiency  of  these  heaters  is,  according  to  tests,  about 
the  same  as  that  of  the  pipe  coil  heaters  and  hence  formulas 
45  and  46  would  apply  in  the  same  way  for  both  kinds. 


PLENUM   WARM   AIR   HEATING 


141 


Table  XVII  gives  values  of  heat  transmission  for  various 
sections,  taken  from  tests  upon  Vento  cast  iron  heaters  set 
up  in  banks,  and  is  added  as  a  means  of  comparison  with 
the  values  quoted  on  the  pipe  coil  heaters. 

TABLE  XVII. 

Rate    of    Transmission    of    Heat,    K,    through    Vento    Coils. 
Steam   227°,  air   entering  at   0°. 

Velocities  of  air  over  coils. 


Sections 

800 

1000 

1200 

1500 

1 

7.6 

8.8 

10. 

11.8 

2 

7.1 

8.2 

9.2 

10.5 

3 

6.6 

7.7 

8.6 

9.7 

4 

6".l 

7.1 

7.9 

9. 

5 

5.6 

6.5 

7-8 

8-8 

6 

5.2 

6. 

6.7 

7-7 

7 

4.8 

5.5 

6-2 

7-1 

In   applying  these   values  of  K  to   formula  45   it  should 

be  remembered  that  to  would  be  used  instead  of K— - 

APPLICATION  1.  Where  Heating  Only  is  Considered. — Refer  ring- 
to  Table  XXV  let  H  for  the  entire  building  be  1483251. 
Then  from  Art.  104,  Q  =  1156935,  by  formula  42,  Hf  =  2966502 
and  by  formula  46,  the  coil  surface  is 

2966502 

=  2222  square  feet. 


R  = 


8.5 


^227  - 


140  +  0 


\ 


With   three    lineal   feet   of   1    inch   pipe    per   square    foot    of 
surface,  we  have  6666  lineal  feet  of  coils  in  the  heater. 

APPLICATION  2.     Where  Ventilation  is  Considered. — Assume  1100 
people  in  the  building  on  a  zero  day  and  Q'  =  2000000,  then, 
H'  =  1483251   +  1.27   X   2000000  =  4023251  and 

4023251 
R  = =3014  sq.  feet  =  9042  lineal  feet. 


8.5^227  - 


142  HEATING  AND  VENTILATION 

This  value  is  probably  the  greatest  amount  that  would 
be  needed.  In  such  a  case,  when  the  rooms  were  supplied 
with  extra  air,  the  register  temperatures  over  the  entire 
building-  may  be  less  than  140  degrees.  Suppose  in  this 
case  the  temperature  to  be,  by  formula  43,  t  =  70  4- 
55  X  1483251  -f-  2000000  =  111°,  then 

4023251 

B  =  =  2760  sq.  ft.  =  8280  lineal  ft. 

Ill  +  0 


/ 

•'('"- 


In  using-  this  formula,  the  value  t  =  140  is  to  be  recom- 
mended wherever  part  of  the  rooms  are  not  provided  with 
extra  amounts  of  ventilating  air.  By  so  doing  the  ducts  and 
registers  may  be  held  down  to  a  more  moderate  size  and 
at  the  same  time  give  a  safer  figure  for  the  heating  surface. 

108.  Approximate  Rules   for  Plenum  Heating   Surfaces: 

— The  following  approximate  rules  are  sometimes  used  in 
checking  up  heating  surface  in  the  coils.  These  are  not 
recommended  and  should  be  used  with  caution. 

Rule  1. — "Allow  one  lineal  foot  of  1  inch  pipe  for  each 
65  to  125  cubic  feet  of  room  space";  65  for  office  buildings, 
schools,  etc.  and  125  for  shops  and  laboratories.  Since  this 
building  has  approximately  500000  cubic  feet  of  room  space, 
it  gives  7700  lineal  feet  of  1  inch  pipe  in  the  heater. 

Rule  2. — "Allow  200  lineal  feet  of  1  inch  pipe  for  each 
1000  cubic  feet  of  air  per  minute  at  a  velocity  of  1500  feet 
per  minute."  Applying  to  the  above  building  when  the  air 
moves  over  the  coils  at  1000  feet  per  minute,  the  heated 
surface  is  only  about  four-fifths  as  valuable  and  would 
require  250  lineal  feet  per  each  1000  cubic  feet  of  air  per 
minute.  This  gives  8333  lineal  feet  of  coils. 

109.  Final    Air    Temperatures: — Since    the    amount    of 
heat  transmitted    is   directly   proportional   to    the   difference 
of  temperature    between   the   two   sides   of   the   metal,    it   is 
readily  seen   that  the   first   coils   in  the   bank  are   the  most 
efficient,    and   that   this   efficiency    drops    oft'    rapidly   as    the 
air  becomes  heated   in  passing   over   the   coils.     Final  tem- 
peratures,  for   different  numbers   of  coil   sections   in  banks, 
have    been    found    by    experiment   and    may    be    taken    from 
Table  XVIII.     See  also  Table  XIV,  page  139. 


PLENUM   WARM   AIR   HEATING 


143 


TABLE  XVIII. 

Temperatures    of    air    upon    leaving    Coils,    steam    227°,    air 
entering-  at   0°. 


Sections 

No.   of 
Bows 

Velocities  of  air  through  coils  in  F.  P.  M. 

800 

1000 

1200 

1500 

1 

4 

42 

33 

28 

23 

2 

8 

71 

62 

56 

52 

3 

12 

96 

87 

80 

75 

4 

16 

119 

108 

101 

93 

5 

20 

136 

125 

116 

108 

6 

24 

153 

140 

131 

120 

7 

28 

169 

155 

143 

131 

8 

32 

183 

166 

154 

141 

These  temperatures  may  be  increased  about  10  per  cent, 
for  20  pounds  gage  pressure. 

Table  XIX  shows  similar  results  quoted  for  the  Vento 
cast  iron  heaters. 


TABLE  XIX. 

Temperatures   of  air  upon   leaving  Vento   Coils,   steam  227°, 
air   entering    at    0°. 


Number 


Velocities  of  air  through  coils  in  F.  P.  M. 


01  STACKS 
deep 

800 

1000 

1200 

1500 

1 

38 

34 

31 

29 

2 

69 

62 

59 

55 

3 

98 

89 

83 

76 

4 

120 

110 

103 

94 

5 

135 

125 

118 

109 

6 

148 

138 

130 

120 

7 

155 

145 

138 

128 

144  HEATING  AND  VENTILATION 

110.  Arrangement  of  Coils  in  Pipe  Heaters: — Coil  sec- 
tions are  arranged  with  2,  3  and  4  rows  of  pipes  per  sec- 
tion. Unless  special  reference  is  made  to  this  point,  the 
latter  value  is  understood.  Having  found  the  total  square 
feet  of  heating  surface  in  the  heater,  obtain  from  the  tem- 
perature tables  the  number  of  sections  deep  the  heater  will 
need  to  be  to  produce  the  desired  temperature,  and  find  the 
number  of  square  feet  of  heating  surface  per  section  and 
per  row  of  coils.  Let  this  latter  value  be  A.  Also  find  the 
net  wind  area  across  the  coils,  assuming,  say,  1000  feet  per 
minute  velocity.  From  the  net  wind  area,  find  the  gross 
cross  sectional  area  of  the  heater  by  the  value. 

Gross  wind  area  =  2.5  times  net  wind  area.  (48) 

From  the  gross  area  the  size  of  the  heater  may  be  selected. 
In  selecting  the  heater,  the  following  check  should  be  ap- 
plied. Find  the  number  of  square  feet  of  heating  surface, 
B,  in  each  row  of  the  coils  as  figured  from  the  gross  area 
and  compare  with  A.  These  must  be  made  to  agree. 

Let  the  net  area  between  the  tubes,  N.  A.,  the  space 
occupied  by  the  tubes,  T.  A.,  and  the  gross  cross  sectional 
wind  area  through  the  tube,  Q.  W.  A.,  be  respectively 

Q  or  Q'  Q  or  Q'  Q  or  Q' 

N.  A.  = ;  T.  A.  = ;  and  G.  W.  A.  =  —         — .  (49) 

60  V  40  V  24  7 

Since  the  cross  sectional  space  T.  A.  occupied  by  the  tubes 
is  to  the  coil  surface  per  row  as  1  :  3.1416,  the  total  coil 
surface  in  one  row  of  tubes  is 

3.1416  (Q  or  Q')  (Q  or  Q') 

B!  =  =    .08   

40  7  7 

Reduced  to  the  basis  of  the  net  area,  N.  A.,  we  have 

Ri  =  4.8  times  N.  A.  (50) 

If  B  is  greater  than  A,  then  the  total  heating  surface 
must  be  increased  in  that  proportion,  since  the  Dumber  of 
sections  cannot  be  less  or  the  final  temperature  will  drop 
below  the  required  degree,  and  the  net  cross  section  cannot 
be  less  or  the  velocity  of  the  air  will  be  greater  than  that 
desired.  On  the  other  hand,  suppose  B  should  be  less  than 
A.  In  that  case  the  total  heating  surface  will  not  change 
from  that  calculated.  Either  B  may  remain  the  same  as 
calculated  and  the  number  of  sections  increased  (if  de- 
sirable) until  all  the  heating  surface  is  accounted  for,  or  A 
may  remain  constant  and  B  may  be  increased.  The  latter 


PLENUM   WARM   AIR   HEATING  145 

method  is  probably  a  better  one  since  it  gives  larger  wind 
areas  and  consequently  reduced  velocities  of  the  air,  which 
in  many  cases  is  desirable,  and  avoids  placing  heating  sur- 
face at  the  rear  of  the  bank  where  it  is  less  efficient. 

Assembled  sections  of  pipe  coil  heaters  are  supplied  by 
manufacturers  from  the  smallest  size  of  3  feet  x  3  feet,  to 
the  largest  size  of  10  feet  x  10  feet;  these  dimensions  being 
those  of  the  gross  cross-sectional  area,  and  noi  dimension*? 
over  all.  Between  the  two  limits,  both  height  and  breadth 
usually  vary  by  6  inch  increments.  For  exact  sizes,  consult 
dimension  tables  in  manufacturers'  catalogs. 

APPLICATION  1.— In  Article  107,  let  R  =  2222,  Q  =  1156935, 
V  =  1000  and  t  =  140;  then  from  Table  XVIII  the  heater  will 
require  24  rows  of  coils  in  depth  to  give  the  required  tem- 
perature. Next  find  RI  =  93  square  feet  of  heating  surface 
per  row,  also 

N.  A.  =  19.7;  T.  A.  =  29.1;  and  Q.  W.  A.  =  48.5. 
Checking  N.  A.  with  an  air  velocity  of  1000  feet  per  min- 
ute gives  1156935  -=-  (60  X  1000)  =19.3  square  feet,  which 
shows  that  the  above  arrangement  is  satisfactory.  Now 
from  the  value  G.  W.  A.  =  48.5  select  a  heater,  say,  6  feet 
x  8  feet. 

APPLICATION  2.— In  article  107,  let  R  =  3014,  Q'  =  2000000, 
7  =  1000  and  t  =  140;  then  as  before,  the  heater  will  need 
24  rows  of  coils.  Find  in  this  case  RI  =  126  and 

N.  A.  —  26.3;  T.  A.  =  39.4;  and  Q.  W.  A.  =  65.7. 
Checking  from  the  volume  of  air  delivered,  obtain 

N.   A.  =   33.3;    T.   A.   =   50;   and  G.   W.  A.   =  83.3. 
From  N.  A.  =  33.3   find  Bx  =  160,   which  shows  that  it  will 

be  necessary  to  increase  the  total  heating  surface  to,  — j-^ — 

LZ6 
X  3014  =  3826  square  feet.     If  it  were  considered  advisable 

to  have  1200  feet  air  velocity  the  heating  surface  per  row 
would  be  reduced  to  135  and  the  temperature,  t,  would  be 
reduced  to  131.  Both  conditions  are  reasonable  and  in 
many  cases  would  be  considered  satisfactory. 

Selecting  the  heater  for  the  gross  area  of  83.3  square 
feet,  from  the  catalog  size,  would  probably  give  a  single 
section  9  feet  x  9  feet  or  a  double  section,  each  part  6 
feet  x  7  feet. 

111.  Arrangement  of  Sections  and  Stacks  in  Vento  Cast 
Iron  Heaters: — Applying  only  to  Case  2,  Art.  107,  let  R  = 


1*6  HEATING  AND  VENTILATION 

3014,  Q'  =  2000000,  V  =  1000  N.  A.  (least  value)  =  33.3,  and  *  = 
140;  also  take  for  cast  iron  heaters 

G.   W.   A.   =   2.3    times    N.    A.  (51) 

From  Table  34,  Appendix,  either  of  the  following  arrange- 
ments will  give  the  necessary  N.  A.  First. — Six  stacks, 
each  620  square  feet,  and  built  up  of  20  sections  50  inches 
high  on  top  of  20  sections,  60  inches  high,  making  a  total 
of  110  inches  high  and  100  inches  long.  Second. — Seven  stacks 
each  612  square  feet,  and  built  up  of  18  sections^  60  inches 
high  on  top  of  18  sections  60  inches  high,  making  a  total 
of  120  inches  high  and  90  inches  long.  With  the  above  ar- 
rangement of,  say,  six  stacks,  Table  XIX  gives  a  possible 
temperature  of  138  degrees,  which  is  slightly  below  what  is 
required.  It  also  gives  a  total  heating  surface  of  approxi- 
mately 25  per  cent,  in  excess  of  the  requirement.  With  this 
arrangement  it  will  be  necessary  to  increase  the  heating 
surface  arbitrarily  or  to  increase  the  air  velocity. 

112.  Use  of  Hot  Water  in  Indirect  Coils: — In  most  cases 
low  pressure  steam  is  used  as  a  heating  medium  in  the  indirect 
coils.    It  is  possible,  however,  to  rse  hot  water  instead,  where 
a  good  supply  is  to  be  had.    In  such  an  arrangement  the  coils 
will  be  figured  from  formula  (45),  using  all  values  the  same 
as  for  steam  excepting  ts,  which  would  be   replaced  by  the 
average  temperature  of  the  water.     The  piping  connections 
and   the   arrangements   of  the   coils   would   follow   the   same 
general  suggestions  as  already  stated. 

113.  Pounds    of    Steam    Condensed    per    Square   Foot    of 
Heating:  Surface  per  Hour: — From  Art.  107  it  is  readily  seen 
that   the   number   of   pounds    of   condensation   per   hour   per 
square  foot  of  surface  in  the   coils  is 

TJt 

m  ~  R  X  Heat  given  off  per  pound  of  condensation. 

APPLICATION. — Let  R  =  3014  and  W  =  4023251;  also  let 
one  pound  of  dry  steam  at  five  pounds  gage  in  condensing 
to  water  at  212  degrees  give  off  1155.6  —  180.9  =  974.7,  say, 
975  B.  t.  u.  (see  Tables  2  and  6,  Appendix.),  then 

4023251 

m  =  =  1.37   pounds. 

3014  X  975 

This  amount  should,  of  course,  be  considered  an  average. 
The  first  and  last  section  in  any  bank  would  vary  above 


PLENUM   WARM   AIR   HEATING  147 

and  below  this  amount  by  as  much  as  50  per  cent,  in  the 
average  plant.  The  first  coils  should  condense  as  much  as  2 
pounds  of  steam  per  square  foot  of  surface  per  hour. 

114.  Pounds  of  Dry  Steam  Needed  in  Excess  of  the 
Exhaust  Steam  Given  off  Prom  the  Engine: — Let  the  heat- 
ing value  of  the  exhaust  steam  from  the  engine  be,  say,  85 
per  cent,  of  that  of  good  dry  steam,  also  let  the  engine 
use  40  pounds  of  dry  steam  per  horse  power  hour  in  driv- 
ing the  fan.  From  Art.  124,  the  engine  will  use  40  X  13.6 
=  544  pounds  of  steam  per  hour  and  the  heating  value  will 
be,  975  X  .85  =  828  B.  t.  u.  per  pound  or  828  X  544  =  450432  B. 
t.  u.  total  per  hour.  Then  4023251  —  450432  =  3572819  B. 
t.  u.,  and  3572819  —  975  —  3664  pounds  of  steam.  The  boiler 
will  then  supply  to  the  engine  and  coils,  3664  +  544  =  4208 
pounds  of  steam  total  and  will  represent,  approximately, 
4208  -r-  30  =  140  boiler  horse  power. 


CHAPTER   XL 


MECHANICAL,    WARM    AIR    HEATING    AND 
VENTILATING     SYSTEM. 


PRINCIPLES     OF    THE    DESIGN,     CONTINUED. 
FANS  AND  FAN  DRIVES. 

115.  Theoretical  Air  Velocity: — The  theoretical  velocity 
of  air  v,  flowing  from  any  pressure,  pa,  to  any  pressure,  pb, 
is  obtained  from  the  general  equation  v  =  ^2gh,  where  v 
is  given  in  feet  per  second,  g  —  32.16  and  Ji  —  head  in  feet 
producing  flow.  This  latter  value  may  be  easily  changed 
from  feet  of  head  to  pounds  pressure  and  vice-versa. 

When  exhausting  air  from  any  enclosed  space  into 
another  space  containing  air  at  a  different  density,  the 
force  which  causes  movement  of  the  air  is  pa  —  p&  —  say, 
PX.  These  recorded  pressures  may  be  taken  by  any  stand- 
ard type  of  pressure  gage  and  show  pressures  above  the 
atmosphere.  When  exhausting  into  the  atmosphere,  the 
value  pb  is  zero  and  pa  =  px.  The  fact  that  a  difference  of 
pressure  exists  between  two  points  indicates  that  there  are 
either  two  actual  columns  (or  equivalent  as  in  Fig.  8)  of 
air  of  different  densities  connected  and  producing  motion, 
or  that,  by  mechanical  means,  a  pressure  difference  is  crea- 
ted which  may  easily  be  reduced  to  an  equivalent  head  h, 
in  feet,  by  dividing  the  pressure  head  by  the  density  of  the 
air,  as 

pressure  difference       pa  —  pi> 


density  d 

Let  pa  —  p&  =  PX  =  ounces  of  pressure  per  square  inch  of 
area  producing  velocity  of  the  air;  also,  let  g  =  acceleration 
due  to  gravity  =  32.16  and  d  =  density,  or  weight,  of  one 
cubic  foot  of  dry  air  at  60  degrees  and  at  atmospheric  pres- 
sure (Table  9,  Appendix,  then,  substituting  in  the  gen- 
eral equation,  we  have 


64.32  X  144p* 

=  87  VP*  (53) 


.0764  X  16 

Since  the  pressure  producing  flow  is  usually  measured 
in  inches  of  water,  tiw,  the  above  can  be  changed  to  equiva- 
lent height  of  air  column  by 

weight  of  water,  per  cu.  ft.  at  given  temp.  X  », 


weight  of  air  at  given  temperature  X  12 


(54) 


PLENUM   WARM   AIR   HEATING  149 

Applying   this   to   dry   air   at    60   degrees    and   water   at   the 
same   temperature    (Tables  9   and   6,   also  Art.    15), 

62.37  Tiw 

h  —  —  68   hw 

12   X    .0764 
then   substituting  in  the   general    equation,   find 


v  =  V64-32   X    68  hw  =  66.2   Vtiw  (55) 

Formula   54    at   the   temperatures    50,    55,    60,    65    and    70 

degrees  respectively,  gives  results  varying  between  v  =  65.5 

V^  for  50  degrees  and  v  —  66.5  \T~^  for  70  degrees,  which 
leads  to  the  approximate  general  rule  that  the  theoretical 
velocity  of  air,  when  measured  by  a  water  column  gage  that  measures 
in  inches  of  water,  equals  sixty-six  times  the  square  root  of  the  height 
of  the  column  in  inches.  Stated  as  a  formula 

v  =    66    ^/^i^^  (56) 

For  calculations  requiring  accuracy,  several  factors 
would  affect  the  final  result;  these  are,  atmospheric  pres- 
sure, humidity,  density  of  the  air  and  temperature  of  the 
air.  Let  the  atmospheric  pressure  and  the  humidity  be 
constant,  since  these  would  affect  the  result  but  little,  and 
take  into  account,  first,  the  density  of  the  air.  Let  the 
pressure  of  the  atmosphere  be  29.92  inches  of  mercury 
(14.7  pounds  =  235  ounces  per  square  inch  area)  then, 
since  the  density  is  proportional  to  the  absolute  pressure, 
the  temperature  remaining  constant,  we  have  from  form- 
ula 53 


64.32  X  144  px  I  px 

=  1336  \  (57) 


235  +  px  »  235  + 

.0764  X  16  X  

235 

Also,    from    the    relation    existing    between     (53)    and    (55), 
formula  57  reduces  to 


/  h* 

v   =   1336   \    (58) 

"    407   +  hw 

From    formulas    57    and    58    the    second    columns    in    Tables 
XX  and  XXI  have  been  calculated. 

APPLICATION. — Air  is  exhausted  from  an  orifice  in  an  air 
duct  into  the  atmosphere.  The  pressure  of  the  air  within 
the  duct  is  one  ounce  by  pressure  gage  or  1.74  inches  by  a 
Pitot  tube.  Assuming  the  air  to  be  dry  and  the  barometer 
standing  at  29.92  inches  when  the  water  in  the  tube  is  60 
degrees,  what  is  the  velocity  of  the  air?  By  the  approxi- 
mate formulas  (53)  and  (56) 


150 


HEATING  AND  VENTILATION 


v  =  87  V3~=  87  F.  P.  8. 
and  v  =  66  yi^'4  =  87.2  F.  P.  8. 
By   formulas    (57)   and   (58) 


1 

v  =  1336  A/ =  86.3  F.  P.  8. 

*      235+1 

/         OT~ 

and  v  =  1336  A/ =  87.1  F.  P.  8. 

*    407  +  1.74 

*  TABLE  XX. 

Column  2  figured  from  formula  57. 


Pressure  In  ounces 
per  sq.  Inch. 

Velocity  of  dry  air  at  6QO  es- 
caping: into   the   atmosphere 
through  any  shaped  orifice  in 
any  pipe  or  reservoir  in  which 
a   griven   pressure    is    main- 
tained. 

Vol.  of  air  in  cu 
ft.  which  may  be 
discharged    in  1 
min.  through  an 
orifice  having  an 
effective  area  of 
discharge    o  f    1 
sq.  inch. 

Ool.  3  -4-  144 

H.  P.  required  to 
move    the  given 
vol.  of  air  under 
the   given    con- 
ditions    o  f    dis- 
charge. 

(  Col.  3  X  Col.  1  ) 

Ft.  per  sec. 

Ft.  per  min. 

16X33000 

5* 

30.80 

1848-00 

12.83 

0.00044 

% 

43.56 

2613.60 

18.15 

000124 

% 

68.27 

8196.20 

22.19 

0.00227 

% 

61-56 

3693-60 

25-65 

0.00349 

ft 

68.79 

4127.40 

28  66 

0.00489 

3/4 

75-35 

4521.00 

31.47 

0.00642 

% 

81.87 

4882.20 

83.90 

0.00809 

1 

86.97 

5218-20 

36-24 

0-00988 

1H  ' 

92.18 

5530.80 

88.41 

0.01178 

IX 

97.18 

5830.80 

40.49 

0.01380 

itt 

101.90 

6114.00 

42.46 

0.01592 

11A 

106.40 

6384.00 

44-83 

0.01814 

itt 

110.82 

6649.20 

46.11 

0.02046 

l3/4 

114-86 

6891.60 

47.86 

0.02284 

1% 

118.85 

7131.00 

49V-52 

9.02533 

2 

122.47 

7348.20 

51.03 

0.02787 

PLENUM   WARM   AIR   HEATING 


151 


TABLE  XXI. 
Column  2  figured  from  formula  58. 


Pressure  in 
inches     o  f 

Velocity  of  dry  air  at  60°  escaping  into  the  atmosphere 
through  any  shaped  orifice  in  any  pipe  or  reservoir  in 
which  a  given  pressure  is  maintained. 

water     per 

sq.  in. 

Peet  per  second 

Feet  per  minute 

.1 

29-04 

3^56.40 

.2 

29.67 

1780  20 

.3 

36.25 

2175-60 

.4 

41.86 

2511.60 

.5 

46.80 

2708  00 

.6 

51.26 

3075.60 

.7 

55  36 

»21.60 

.8 

59-10 

3516-00 

.9 

62.60 

3756.00 

1. 

66.14 

3968.40 

1.1 

69-36 

4161-60 

1.2 

72.44 

4346.40 

13 

75-39 

4523.40 

1.4 

78-21 

4692.60 

1.5 

80.96 

4857-60 

1  6 

83.59 

5015.40 

1.7 

86-16 

5169.60 

1.8 

88-65 

5819.00 

1.9 

91-27 

5476.20 

2. 

93.42 

5605-20 

2.1 

95-72 

5743-20 

2  2 

97  96 

5877  60 

2  3 

100.15 

6009-00 

2.4 

102.29 

6137.40 

25 

104.39 

6263.40 

2  6 

106.43 

6885-80 

2.7 

108-46 

6507  60 

2.8 

110.43 

6<V25.80 

2.9 

112-37 

8742.20 

3. 

114.28 

6856-80 

3  1 

116.15 

6969.00 

32 

118.00 

7  s).00 

3.3 

119.81 

7188.60 

34 

121.60 

7296.00 

3-5 

123.36 

7401-60 

Finally,  after  considering  the  change  of  velocity  that 
takes  place  when  the  density  changes  with  a  constant  tem- 
perature, let  the  temperature  change.  With  a  constant 
pressure,  the  volume  changes  with  the  absolute  temperature 


152 


HEATING  AND  VENTILATION 


(460  +  f).  From  this  basis  the  values  given  in  the  second 
columns  of  Tables  XX  and  XXI,  which  were  figured  for  60 
degrees,  would  be  multiplied  by  the  relative  factors  for 
the  given  temperature  as  expressed  in  column  two,  Table 
XXII,  to  obtain  the  velocity  of  the  exhausting  air  at  any 
pressure  and  any  temperature.  Having  found  the  data 
from  Column  2,  find  other  points  of  information  concerning 
velocities,  pressures,  "weights  and  horse  powers  in  moving 
air  by  multiplying  by  the  factors  as  given  in  the  respective 
columns. 

TABLE  XXII. 


Factor  for  rel- 

ip. in  Degrees. 

ative    vel.     at 
same  pressure 
also    relative 
powers     to 
move      same 
vol.  of   air    at 
same  vel.  = 

Factor     for 
relative  pres- 
sure, also  wt. 
of  air  moved 
at  same  ve- 
locity = 

4600  +  600 

Factor  for  rel- 
ative   vel.    to 
move     same 
wt.  of  air  also 
relative     pres- 
sure    to     pro- 
duce the  vel.  to 
move  same  wt. 

Factor  for  rel- 
ative power  to 
move      same 
wt.    of    air    at 
vel.  in  column 
4  and  pressure 
in  column  4  = 
factor    in    col- 

ti 

G> 

Vwt.  at  any  T 

T 

of  air  = 

umn  4  squared 

t* 

Wt.  at  4600  +  eoo 

1  •+-  Col.  3. 

30 

•  97 

1.07 

.93 

.87 

40 

•  98 

1.04 

.96 

.92 

50 

.99 

1.02 

.98 

.96 

60 

1.00 

1.00 

.00 

1.00 

70 

1.01 

.98 

.02 

1.04 

80 

1.02 

.96 

.04 

1.08 

90 

1.03 

•  94 

-06 

1.13 

100 

1.04 

.92 

.09 

1.19 

125 

1.06 

.89 

.12 

1.25 

150 

1  08 

.85 

.18 

1.39 

175 

1.10 

.82 

.22 

1.49 

200 

1  13 

•  79 

.27 

1.61 

250 

1.17 

.78 

•  S7 

1.88 

800 

1.21 

.68 

.47 

2.16 

350 

1.25 

.64 

.56 

2.43 

400 

1.28 

.60 

.67 

2.79 

500 

1.36 

.54 

.85 

3.42 

600 

1.43 

.49 

2.04 

4.16 

700 

1.49 

.45 

2.22 

4.93 

800 

1.56 

.41 

2.44 

5.95 

116.     Actual  Amount  of  Air  Exhausted: — When  air  of  any 

pressure  is  exhausted  from  one  receptacle  to  another  through 
an  orifice,  the  actual  velocity  remains  about  the  same  as 
the  theoretical  velocity,  being  slightly  reduced  by  friction, 
but  the  volume  of  air  discharged  is  greatly  reduced  because 


PLENUM   WARM   AIR   HEATING 


153 


of  the  contraction  of  the  stream  just  as  it  leaves  the  ori- 
fice. The  greatest  contraction  or  least  size  of  the  jet  is 
located  from  the  orifice  a  distance  of  about  one-half  the  diam- 
eter of  the  opening.  A  round  opening  is  the  most  efficient. 
Since  the  velocity  is  slightly  reduced  and  the  effective  area 
of  the  opening  reduced  a  still  greater  amount,  the  actual 
amount  of  air  exhausted  in  any  given  time  would  be  found 
by  multiplying  the  theoretical  amount  by  a  constant  which 
is  the  product  of  the  coefficient  of  reduced  velocity  and  the 
coefficient  of  reduced  area.  From  tests  the  following  ap- 
proximate values  are  quoted  by  the  Sturtevant  Company 
in  Mechanical  Draft,  page  152. 

Orifice    in    a   thin    plate,  .56 

Short  cylindrical  pipe,  .75 

Rounded  off  conical  mouth  piece,          .98 
Conical    pipe,   angle   of   convergence 
about  6°,  .92 

117.  Results  of  Tests  to  Determine  the  Relation  be- 
tween Pressure  and  Velocity: — In  Power,  Heating  and  Ven- 
tilation, page  536,  Mr.  Hubbard  gives  curves,  Fig.  71,  show- 
ing the  ratio  of  the  air-velocity  pressure  to  the  peripheral- 
velocity  pressure  in  fan  experiments;  also,  between  the  air- 
velocity  pressure  and  the  dynamic  pressure  for  degrees  of 
discharge  opening  varying  from  40  per  cent,  to  100  per 
cent,  or  full  opening. 


100 


10 


20        30 


50        60        70        80        90       100 


RATIO  OF  EFFECT. 

Fig.  71. 


154  HEATING  AND  VENTILATION 

In  the  tests  a  pipe,  the  size  of  the  fan  outlet  and  about 
12  feet  in  length,  was  attached  directly  to  the  casing  and 
provided  with  a  gate  at  the  outer  end  to  allow  for  any  de- 
gree of  opening.  The  fan  was  run  at  constant  speed  and 
the  dynamic  and  static  pressures  were  measured  about  mid- 
way of  the  pipe  at  full  opening.  Then  the  opening  was 
changed  by  10  per  cent,  reductions  and  readings  taken.  The 
pressure,  corresponding  to  the  peripheral-velocity  pressure, 
was  found  by  formula  56  and  the  results  of  the  test  were 
plotted  in  curves  showing  ratios  to  this  peripheral-velocity 
pressure.  As  an  illustration,  the  relation  between  the  air 
velocity  pressure  to  the  peripheral-velocity  pressure  for 
full  opening  and  discharging  into  free  air  is  .43.  Since 
the  velocities  always  vary  as  the  square  root  of  the  pres- 
sure (v  —  \J2gh),  we  find  that  the  velocities  in  this  case  vary 
as  V  *43  —  -65-  This  shows  that  for  this  one  condition,  the 
air  velocity  at  the  free  opening  =  .65  times  the  peripheral 
velocity  of  the  fan.  For  methods  of  measuring  velocity 
and  pressure,  see  Art.  15. 

118.  Work  Performed  and  Horse  Power  Consumed  in 
Moving  Air: — The  foot  pounds  of  work  performed  in  moving 
air  equals  the  product  of  the  moving  force  into  the  distance 
moved  through  in  any  given  time.  Let  pa  —  pi>  =  PX  = 
moving  force  of  the  air  in  ounces  per  square  inch  and  A  = 
cross-sectional  area  of  current  in  square  inches,  then  the 
pounds  per  square  inch  will  be  px  -f-  16,  and  the  foot  pounds 
of  work,  W,  and  the  horse  power,  H.  P.,  absorbed  per  min- 
ute by  the  current  of  air  in  being  moved,  will  be 

60  px  A  v 

W  = =  3.75  px  A  v  (59) 

16 
3.75  px  A  v 

E.  P.  =  =   .000114   px  A  v  (60) 

33000 

This  formula  may  be  stated  in  terms  of  the  cubic  feet  of 
air  discharged  per  minute.  Take  the  relation  between  PJ> 
and  ftw  at  60  degrees  as  12  p*  =  16  X  .433  hw;  also,  A  X  v  = 
144  Q'  when  Q'  =  cubic  feet  of  air  discharged  per  second 
and,  from  formula  (58),  Jiw  —  v2  -4-  4356,  then  by  substituting 
in  formula  60 

3.75  X   .577  X  v2  X  144  Q' 

H.  P.  =  : =   .0000022  v2  Q'        (61) 

4356  X  33000 
APPLICATION  1. — Let  the  effective  area  of  a  stream  of  dry 

air  at  60  degrees,  exhausting  between  the  pressures  of  pa  = 


PLENUM   WARM  AIR   HEATING  155 

\^/z  ounces  and  po  =  %  ounce,  be  400  square  inches.  What  is 
the  work  performed  per  minute  and  the  horse  power  con- 
sumed? 

TF  =  3.75  X  (1%  —  %)  X  400  X  .87  =  1305  foot  pounds, 
and  H.  P.  =  .000114  X  (1%  —  %)  X  400  X  87  =  .1487. 

APPLICATION   2. — A  fan   is   delivering   1000000   cubic   feet   of 
air   per    hour    to    a    heating    system   with    a   pressure    of   % 
ounce.     What  is  the  theoretical  horse  power  of  the  fan? 
H.  P.  =   .0000022    X    (74. 5)2  X    277  =   3.7 

119.  Actual   Horse   Power    Consumed   in   Moving  Air   by 
Blower  Fans: — The  theoretical  horse  power  of  a  fan  is  that 
horse  power  necessary  to  move  the  air.     This  amount  is  al- 
ways  exceeded,  however,   because  of  the   inefficiency  of  the 
blower.     Let  E  =  efficiency  of  the  blower,  then  formulas   60 
and  61  become 

.000114  px  A  v 

H.  P.  =  (62) 

E 
.0000022  v*  Qe 

H.  P.  =  (63) 

E 

The  value  E  varies  with  the  peripheral  velocity  and 
the  percentage  of  free  outlet.  When  subjected  to  ordinary 
service,  the  efficiency  of  the  fan  or  blower  may  vary  any- 
where from  10  to  40  per  cent.  Probably  a  safe  figure,  for 
an  efficiency  not  definitely  known,  is  30  per  cent,  for  cen- 
trifugal fans  in  heating  systems,  (see  also  Art.  123.) 

120.  Carpenter's    Practical    Rules: — Many    experiments 
have  been  run  upon  blower  fans  to  determine  their  capacity 
in  cubic  feet  of  air  delivered  per  minute   and  to  determine 
the  horse  power   necessary  to  move   this   air.      Probably  as 
satisfactory  as  any  are  the  rules  quoted  by  Prof.  Carpenter 
in  H.  &  V.  B.,  Art.  162,  as  follows: 

Rule.  "The  capacity  of  fans,  expressed  in  cubic  feet  of 
air  delivered  per  minute,  is  equal  to  the  cube  of  the  diam- 
eter of  the  fan  wheel  in  feet  multiplied  by  the  number  of 
revolutions,  multiplied  by  a  coefficient  having  the  follow- 
ing approximate  value:  For  fan  with  single  inlet  delivering 
air  without  pressure,  0.6;  delivering  air  with  pressure  of 
one  inch,  0.5;  delivering  air  with  pressure  of  one  ounce,  0.4; 
for  fans  with  double  inlets,  the  coefficient  should  be  in- 
creased about  50  per  cent.  For  practical  purposes  of  ven- 
tilation, the  capacity  of  a  fan  in  cubic  feet  per  revolution 
will  equal  .4  the  cube  of  the  diameter  in  feet." 

Rule.     "The  delivered  horse  power  required  for  a  given 


156 


HEATING  AND  VENTILATION 


fan  or  blower  is  equal  to  the  5th  power  of  the  diameter  in 
feet,  multiplied  by  the  cube  of  the  number  of  revolutions 
per  second,  divided  by  one  million  and  multiplied  by  one  of 
the  following'  coefficients :  For  free  delivery,  30;  for  de- 
livery, against  one  ounce  pressure,  20;  for  delivery  against 
two  ounces  of  pressure,  10." 

The  two  above  rules  stated  as  formulas  are  as  follows: 


where  D  =  the  diameter 

for  pressure   of  one  ounce,    .5 

.  6   for  no  pressure. 


Cu.  ft.  of  air  per  min. 

C  X  R.  P.  M. 
in   feet  and   C  = 


(64) 


the,  coefficient,    .4 
for  pressure  of  one  inch  and 


D5    (R.  P,   fif.)3   X   C 

H.  P.  =  (65) 

1000000 

where  C  =  30  for  open  flow,  20  for  one  ounce  and  10  for  two 
ounces  pressure  respectively.  These  two  rules  may  be 
checked  up  by  sizes  obtained  from  catalogs.  They  give, 
however,  in  ordinary  calculations,  very  close  approxima- 
tions. 

121.  If  it  is  Desired  to  Obtain  the  Approximate  Sizes  of 
the  Different  Parts  of  the  Fan  \Vheel  and  Opening,  the  same 
can  be  found  by  the  following  table  which  gives  good  aver- 
age values  for  the  standard  makes  of  fans.  For  more  com- 
plete data  see  tables  in  catalogs. 

TABLE    XXIII. 


Diameter  Wheel 
Diameter  Inlet,   Single 
Diameter  Inlet,  Double 
Dimensions  of  Exhaust 
Width   of  wheel  at  outer  circumference 
Least  radial  distance  from  wheel  to 
casing 
Maximum  radial  distance  from  wheel 
to    casing 

D 

.66  D 
.5     D 
6     D   X 
.5     D      to 

.08  D      to 
.50  D      to 

.5  D 
.6  D 

.16D 
1.      D 

to    casing                                                         .50  D      to  1.     D 
Least  side  distance  from  wheel  to  casing.  05  D      to      .  08D 

Occupied  Space 
of 
Full  Housing  Fan 

Discharge   Vert. 

Discharge  Horiz 

Length 
Width 
Height 

1.7    D 
.7    D 
1.5    D 

1.5    D 

.7    D 
1.7    D 

PLENUM   WARM   AIR   HEATING  157 

122.  Fan  Drives: — Fans,  for  heating  and  ventilating 
purposes,  may  be  driven  by  simple  horizontal  or  vertical- 
throttling  or  automatic  steam  engines,  or  by  electric  mo- 
tors; the  principal  advantage  of  the  latter  being  the  clean- 
liness. In  either  case  the  power  may  be  direct-  connected 
or  belt-connected  to  the  fan.  Direct-connected  fans  make 
a  very  neat  arrangement,  but  they  require  slow  speed 
engines  or  motors,  occasionally  making  them  so  large  as  to 
be  prohibitive.  Where  engines  are  used,  any  unusual  noise 
or  pounding  in  the  parts  is  frequently  carried  through  the 
fan  to  the  air  current  and  up  to  the  rooms.  Belted  drives 
may  run  at  higher  speeds  but  they  must  of  necessity  be  set 
off  from  the  fan  ten  feet  or  more  to  get  good  belt  contact. 
Noiseless  chain  drives  will  permit  the  same  reductions  of 
speed  and  will  allow  the  engine  to  be  set  very  close  to  the 
fan.  Where  a  reduction  is  made  in  the  space  between  the 
engine  and  the  fan,  it  had  best  be  made  in  the  last  named 
way. 

In  deciding  between  an  engine  drive  and  a  motor  drive 
for  use  with  steam  coils,  the  amount  of  steam  used  in  the 
engine  should  not  be  considered  a  loss,  since  this  is  all 
exhausted  into  the  heater  coils  and  is  used  instead  of  live 
steam  from  the  boilers.  An  engine  of  high  efficiency  is  not 
so  essential  either,  unless  the  exhaust  steam  cannot  be 
used.  Enclosed  engines  running  in  oil  are  preferred  when 
used  on  high  speeds.  The  belt  when  used  should,  if  pos- 
sible, have  the  tight  side  below  to  increase  the  arc  of 
contact. 

Electric  motors  have  more  quiet  action  and  in  special 
cases  should  be  specified.  They  would  generally  be  speci- 
fied for  installations  where  the  exhaust  steam  could  not 
be  used,  as  in  systems  for  ventilating  only.  This  method  of 
driving  the  fan  is  more  satisfactory  in  many  ways  but  its 
operation  is  usually  more  expensive.  Direct  current  motors 
are  desirable,  whenever  they  can  be  applied,  because  of  the 
convenience  in  obtaining  changes  of  speed  and  because  the 
motors  may  easily  be  direct-connected  to  the  fan.  Alter- 
nating current  motors  are  used  but  they  usually  run  at 
higher  speeds,  requiring  reduction  drives  and  are  not  so 
satisfactory  in  regulation. 

123.  Speed  of  the  Pan: — A  blower  fan,  exhausting  into 
the  open  air,  will  deliver  air  with  a  linear  velocity  slightly 


158 


HEATING  AND  VENTILATION 


below  the  peripheral  velocity  of  the  fan  blades,  but  if  this 
same  fan  be  connected  to  a  system  of  ducts  and  heater 
coils,  the  linear  velocity  of  the  air  becomes  much  less  be- 
cause of  the  increased  resistance  and  the  lag  or  slip  that 
takes  place  between  the  fan  blades  and  the  moving  air.  In 
the  average  heating  system  this  slip  may  be  as  great  as 
40  to  50  per  cent.  See  Art.  119.  It  is  customary,  therefore, 
in  applying  blowers  to  heating  systems,  to  consider  the 
linear  velocity  of  the  air  as  it  leaves  the  fan  to  be  one- 
half  that  of  the  periphery  of  the  fan  blades.  Since  the 
velocity  of  the  air  upon  delivery  from  the  fan  should  not 
exceed  1800  to  2500  feet  per  minute,  the  outer  point  on  the 
fan  blades  should  not  be  expected  to  move  faster  than  3600 
to  5000  feet  per  minute.  Knowing  this  peripheral  velocity, 
the  revolutions  per  minute  may  be  selected  and  the  diameter 
obtained. 

In  all  direct-connected  fans  the  revolutions  per  minute 
must  agree  with  that  of  the  engine  or  motor.  In  belted  fans, 
however,  this  restriction  need  not  apply.  It  is  found  that 
ordinary  blower  fans  running  at  high  speeds  are  very  noisy 
and  so  practice  has  determined  largely  the  number  of  rev- 
olutions to  use.  These  may  be  taken  as  in  the  following 
table. 

TABLE  XXIV. 
Speeds    of    Blower    Fans    in   R.   P.    M. 


Diameter  of 
wheel 
in  inches 

Differential  Pressures 

Va   oz 

y4  oz. 

loz. 

IK    oz. 

2   oz. 

18 

700 

900 

1100 

1300 

1500 

24 

650 

700 

825 

1000 

1150 

86 

400 

500 

575 

675 

800 

48 

300 

375 

400 

500 

600 

60 

225 

290 

340 

400 

475 

72 

175 

230 

290 

340 

40C 

96 

150 

175 

200 

250 

300 

120 

125 

150 

175 

200 

225 

180 

75 

100 

110 

140 

160 

PLENUM   WARM   AIR   HEATING  159 

In  some  types  of  fans,  the  number  of  blades  is  in- 
creased and  the  depth  of  the  blades  is  diminished,  making 
the  operation  of  the  fan  somewhat  similar  to  that  of  the 
steam  turbine.  These  fans  take  the  name  of  turbine  fana 
and  from  tests  seem  to  show  increased  efficiency.  As  a 
result,  this  type  of  fan  for  the  same  work  may  be  smaller 
for  the  same  number  of  revolutions  or  it  may  be  the  same 
diameter  and  have  a  reduced  speed.  The  above  table  does 
not  apply  to  this  type  of  fan,  the  speeds  of  which  will 
average  very  closely  to  70  per  cent,  of  those  in  the  table. 

124.  Size  of  the  Engine: — In  obtaining1  the  size  of  the 
engine,  it  will  be  necessary  first  to  assume  the  horse  power. 
This  had  better  be  taken  as  a  certain  ratio  to  that  of  the 
fan.  Probably  a  safe  value  would  be 

H.  P.  of  the  engine  =  3  H.  P.  of  the  fan  (66) 

Having  obtained  the  horse  power  of  the  engine,  it  will 
next  be  necessary  to  find  the  size  of  the  cylinder.  Let  PI  = 
the  absolute  initial  pressure  of  the  steam  in  the  cylinder, 
i.  e.,  atmospheric  pressure  +  gage  pressure,  and  r  =  number 
of  the  steam  expansions  in  the  cylinder,  i.  e.,  reciprocal  of 
the  per  cent,  of  cut-off.  The  cut-off  allowed  for  high  speed 
engines  in  economical  power  service,  approximates  25  per 
cent,  of  the  stroke,  but  in  engines  for  blower  work  this 
may  be  taken  at  50  per  cent,  or  half  stroke.  Find  the 
mean  effective  pressure,  PI,  by  the  formula, 

1  +  hyperbolic  logarithm  of  r 

P!  =  pa back  pressure  (67) 

r 

Next,  let  I  =  length  of  the  stroke  in  inches  and  N  =•  number 
of  revolutions  per  minute  and  apply  the  formula 

2px  I  AN 

H.  P.  =  (68) 

12   X  33000 

and  find  A,  the  area  of  the  cylinder,  from  which  obtain  d, 
the  diameter  of  the  cylinder.  In  applying  formula  (68)  it 
will  b'e  necessary  to  assume  I,  This,  for  engines  operating 
blowers,  may  be  taken, 

2    I  N  =  200    to    400 

Formula  67  assumes  that  the  steam  in  the  cylinder  expands 
according  to  the  hyperbolic  curve,  pv  =  p'v'.  For  values 
of  hyperbolic  or  Naperian  logarithms  see  Table  3,  Appendix. 


160  HEATING  AND  VENTILATION 

It  also  assumes  no  loss  in  the  recompression  of 
the  steam  in  the  cylinder.  Both  assumptions  are  only 
approximately  correct,  but  the  errors  are  slight  and  to  a 
certain  degree,  tend  to  neutralize  each  other,  hence  the 
final  results  from  this  formula  are  near  enough  to  be  used 
for  approximate  calculations.  For  such  work  as  this,  r 
may  be  taken  from  2  to  3,  the  former  being  probably  pre- 
ferred. The  back  pressure  should  not  be  taken  higher  than, 
say,  5  pounds  gage  (19.7  pounds  absolute),  since  this  is 
determined  by  the  pressure  in  the  coils  carrying  exhaust 
steam.  This  pressure,  in  ordinary  service,  usually  drops 
more  nearly  to  atmospheric  pressure. 

In  finding  the  diameter  and  length  of  the  stroke  of  the 
cylinder,  it  may  be  necessary  to  make  two  or  more  trial 
applications  before  a  good  size  can  be  obtained.  Owing 
to  the  fact  that  the  initial  steam  pressure  is  frequently 
low,  say  not  to  exceed  40  or  50  pounds,  the  mean  effective 
pressure  is  small,  thus  calling  for  a  cylinder  of  large 
diameter.  In  such  cases,  the  diameter  of  the  cylinder  may 
be  greater  than  the  length  of  the  stroke.  In  cases,  how- 
ever, where  high  pressure  steam  is  used,  say  100  pounds 
gage,  the  diameter  of  the  cylinder  would  be  less  than  the 
length  of  the  stroke. 

APPLICATION  1. — Assume  the  following  to  fit  the  design 
shown  in  Figs.  74,  75  and  76:  good,  dry  steam  from  the 
boiler  to  the  engine  at  100  pounds  gage  pressure;  direct- 
connected  engine  to  fan,  running  at  200  revolutions  per 
minute  and  delivering  2000000  cubic  feet  of  air  per  hour 
to  the  building  at  one  ounce  pressure;  steam  cut-off  in  the 
cylinder  at  one-third  stroke  and  used  in  the  coils  at  5 
pounds  gage  pressure;  find  the  sizes  and  horse  powers  of  the 
fan  and  engine  unit.  Applying  formulas  (64),  (65),  (66), 
(67)  and  (68), 


2000000 

D.  of  fan  =  \l =7.5  feet. 

60  X   .4  X  200 

(7.5)5X  (3.3S)3  X  20 

H.  P.   of  fan  = =  10.2 

1000000 
H.  P.  of  Engine  =  J  X  10.2  =  13.6 

/     1  +  1.0986     \ 
Pi  =   115   I  )  —  19.9   =   60.5   pounds   per 


250 

square  inch.  Now  if  2  I  N  =  250,  then  I  = =  .625  feet  = 

400 


PLENUM   WARM   AIR   HEATING  161 

13.6  X  12  X  33000 

7.5    inches    and   A.  =  =    29    square 

2  X   60.4  X  7.5  X  200 

inches   =   6%    inches    diameter.      The    engine   would   be,    say, 
6%  inches  X   7V2  inches,  at  200  R.  P.  M. 

APPLICATION  2. — Assuming  the  values  as  in  application  1, 
excepting  that  the  steam  is  taken  from  a  conduit  main 
under  a  pressure  of,  say,  30  pounds  per  square  inch  gage, 
that  2  I  N  =  300,  and  that  the  steam  cut-off  in  the  cylinder 
is  at  one-half  stroke.  Then,  as  before,  D  of  fan  =  7.5  feet; 
H.  P.  of  fan  =  10.2;  and  H.  P.  of  the  engine  =  13.6;  the 
mean  effective  pressure  is,  however, 


/     1  +   .6931    \ 
Pi  =  45  ( J  —  19.9  =  18. 


2  pounds  per  sq.  in. 


13.6  X  12  X  33000 

and  A  =  =  82  square  inches. 

2  X  18.2  X  9  X  200 

Size  of  the  engine  would  be  10%  inches  X  9  inches,  at  200 
R.  P.  M. 

125.      Piping   Connections   around   Heater   and  Engine: — 

Where  the  fans  are  run  by  steam  power  it  is  considered 
best  to  reduce  the  pressure  of  the  steam  by  a  pressure  re- 
ducing valve  before  allowing  the  live  steam  to  enter  the 
coils.  Where  this  reduction  is  made  to  5  pounds  or  below, 
it  may  be  entered  into  the  same  main  with  the  exhaust 
steam  from  the  engine,  if  desired;  the  back  pressure  valve 
on  the  exhaust  steam  line  providing  an  outlet  to  the  at- 
mosphere in  case  the  pressure,  for  some  reason,  should  run 
above  the  5  pounds  allowable  back  pressure.  If  the  value 
of  the  back  pressure  is  increased  much  above  5  pounds, 
the  efficiency  of  the  engine  is  seriously  affected.  In  many 
installations  where  the  condensation  from  the  live  steam 
is  desired  free  from  oil,  a  certain  number  of  coils,  only,  are 
tapped  for  exhaust  steam  and  this  condensation  trapped  to 
a  waste  or  sewer,  the  other  coils  delivering  to  a  receiver 
of  some  sort  for  boiler  feed  or  other  purposes  as  may  be 
required. 

Every  system  should  be  fully  equipped  with  pressure 
reducing  valves,  back  pressure  valves,  traps  and  a  sufficient 
number  of  globe  or  gate  valves  on  the  steam  supply,  and  of 
gate  valves  on  the  returns  to  make  the  system  flexible  and 
responsive  to  varying  demands,  at  the  will  of  the  operator. 
Figs.  72  and  73  show  a  typical  plan  and  elevation  for  such 


162 


HEATING  AND  VENTILATION 


connections.  Some  engineers  advocate  lifting  the  returns 
about  20  or  30  inches  as  shown  at  A  and  B  to  form  a  wate* 
seal  for  each  section,  thus  making  them  independent  in 
their  action.  This,  in  some  cases  where  the  coils  are  very 
deep,  would,  no  doubt,  be  a  benefit. 

3TBACH   PRESS.  VA'^VE 


k  -  !&=r===35==r=^^ 


3EPARATOF1. 


CHECK 


BO/LER 


Fig.    72. 


' 

*•  BACK  PRCS3   VALVE                                                           ifPReSS.Rt 

CX    3TEAM 

L.IVF  JT| 

c 

!t 

UJ                        o  * 
Q                        "> 

w                   <J| 

(C  * 

I                    *lu 

.A?    c 

1 

1 

1 

1 

^         ^ 

«  i 

T 

GATC    VALV/E5 

4  I""" 


Fig.   73. 

126.  Application  to  School  Building: — The  three  follow- 
ing figures  and  summary  show  the  results  of  an  ap- 
plication of  the  above  to  a  school  building.  The  summary, 


PLENUM   WARM   AIR   HEATING  163 

Table  XXV,  gives  in  compact  form  such  calculated  results 
as  admit  of  tabulation.  Most  of  the  applications  throughout 
Chapters  IX,  X  and  XI,  also  refer  to  this  same  building. 

The  plans  show  the  double-duct  system,  with  plenum 
chamber  and  ducts  laid  just  below  the  basement  floor.  The 
small  arrows  show  the  heat  registers  and  vent  registers  for 
each  room.  The  same  stack  which  served  as  a  heat  carrier 
to  the  room  on  one  floor  serves  as  the  vent  stack  for  the 
corresponding  room  on  the  floor  above,  there  being,  of  course, 
a  horizontal  cut-off  between  them.  The  cut-off  at  the  heat 
register  should  be  so  curved  as  to  throw  the  current  of 
heated  air  into  the  room  with  the  least  possible  friction  or 
eddy  currents,  as  shown  in  P  ig.  20. 


164 


HEATING  AND  VENTILATION 


TABLE     XXV. 

Data  Sheet  for  Figs.  74,  75,  76. 


Room 

n 

Heat  loss  In  B.t.u.  per 
hour  from  room  not 
counting  ventilation. 

Heat  loss  counting  ex- 
posure 

Per  cent,  added 

Cubic  feet  of  air  needed 
per  hour  as  a  heat 
carrier 

No.  of  reg'ters  install'd 

II 

«H  ° 

ofl 

o3  • 

<D  O1 
§* 

^a 

<S>  -1-1 

flg 

p 

Size  of  registers  in 
inches 

Size  of  stack  in  inches. 

1.  . 

1 
H 

51,520 

74,200 

40,185 
57,876 

2 

322 

18x20 

13x13 

2... 

8 

1H 
\% 

ll/2 
1% 

29,400 
86,260 
42,210 
35,350 

22,932 
28,283 
32,923 
27,573 

1 
1 
1 
1 

184 
226 
263 
220 

17x18 
17x21 
17x25 
17x21 

17x13 
17x13 
17x18 
17x18 

4... 

5 

6... 

7 

8... 

1H 
\% 

\% 

1(5,520 
16,520 
42,210 

12,885 
12,885 
32,923 

1 
1 
1 

103 
103 
263 

13x13 
13x13 
17x25 

13x  8 
13x  8 
17x13 

9 

10  

Totals. 

344,190 

268,466 

11 

\ 
I1/* 
\% 

VA 
\% 

1V4 

llA 

81,130 
115,430 
40,500 
55,370 
63,840 
48,440 
51,940 
23,660 
23,660 
63,840 

63,281 
99,039 
34,775 
47,507 
54,775 
89,672 
40,513 
19,377 
18,455 
49,795 

2 
4 
1 
2 
2 
1 
2 
1 
1 
2 

506 
792 
278 
380 
488 
317 
824 
155 
148 
898 

17x24 
17x18 
17x26 
17x18 
17x21 
17x80 
13x20 
13x20 
13x20 
17x18 

17x13 
17x13 
17x18 
17x13 
17x18 
17x13 
13x18 
13x18 
13x13 
17x13 

12... 

126,973 
44,583 
60,907 
70,224 
50,862 

10 
10 
10 
10 
5 

13 

14.  . 

15  
16 

17 

18 

24,843 

5 

19 

20  

Totals. 

540,100 

467,189 

21... 
22  

23... 
24  
25  

26  
27  
28.  
29.  
30  

l 
1 
1 
1 
1 
1 

IIA 
i 

81,130 
17,150 
103,460 
17,150 
31,900 
48,580 
93,030 
28,420 
37,380 
54,110 

63,281 
13,377 
88,764 
13,377 
27,447 
41,682 
79,819 
22,163 
29,156 
42,206 

2 
1 
2 
1 
1 
2 
2 
2 
1 
2 

506 
107 
710 
107 
220 
333 
638 
177 
233 
338 

17x24 
13x13 
21x28 
13x18 
17x21 
13x20 
17x80 
13x15 
17x21 
13x20 

17x13 
13x  8 
17x13 
18x  8 
17x13 
13x18 
17x13 
13x  8 
17x18 
13x13 

113,800 

10 

35,189 
53,438 
102,333 

10 
10 
10 

Totals. 

598,961 

421,272 

Vent  registers  taken  same  size  as  heat  registers.    For  sizes  of 
engine  .fan,  heater  coils,  etc.,  see  applications  under  these  heads. 


PLENUM   WARM   AIR  HEATING 


165 


166 


HEATING  AND  VENTILATION 


gs  g 

5?     PS 


h=|   kd    |^JD^=J '  t=4"B" 


C 


.M    M    M 


Fig.   75. 


PLENUM    WARM   AIR    HEATING 


167 


OQ 


M=J   i^j  •^T-^        UT  w*   £=-€: 


>=l   ^LEL£Jsa- 


>Jj 
o  a 


st 


I 


Fig.   76. 


168  HEATING  AND  VENTILATION 


REFERENCES. 

References  on  3Iechanical  Warm  Air  Heating. 

TECHNICAL  BOOKS. 

Snow,  Furnace  Heating,  p.  99.  Monroe,  Steam  Heat.  &  Vent.,  p. 
124.  Carpenter,  Heating  and  Ventilating  Buildings,  p.  333.  Hub- 
bard,  Power,  Heating  and  Ventilating,  pages  525  and  551. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Ventilating  and  Air  Washing  Appar- 
atus installed  in  the  Sterling-Welch  Building,,  Cleveland, 
O.,  Jan.  1910,  p.  38.  Steam  Heat,  and  Vent.  Plant  Required 
for  Addition  to  the  Hotel  Astor,  New  York,  March  1910,  p.  27. 
Heating  and  Ventilating  Plant  of  the  Boston  Safe  Deposit 
and  Trust  Company's  Building,  C.  L.  Hubbard,  April  1910,  p. 
37.  Heating  and  Ventilating  Installation  on  the  Burnet  St. 
School,  Newark,  N.  J.,  Jan.  1909,  p.  20.  Heating  and  Venti- 
lating the  New  Jersey  State  Reformatory,  Sept.  1909,  p. 
27.  Comparison  of  Heat,  and  Vent.  Plants  Installed  in 
Chicago  Schools  and  Buildings  at  Various  Periods,  T.  J. 
Waters,  June  1906,  p.  14.  Heating  and  Ventilating  of  Schools, 
F.  G.  McCann,  June  1906,  p.  11.  The  Heating  and  Ventilation 
of  Schools,  Dec.  1904,  p.  1;  March  1905,  p.  4;  Sept.  1905,  p.  1; 
Oct.  1905,  p.  5.  Note:  The  last  two  articles  taken  together 
comprise  a  complete  series  of  the  heating  and  ventilating 
of  the  schools  of  New  York  City.  Machinery.  Fans,  C.  L. 
Hubbard,  Oct.  1905,  p.  49;  Nov.  1905,  p.  109;  Dec.  1905,  p.  165. 
Heaters  for  Hot  Blast  and  Ventilation,  C.  L.  Hubbard,  March 
1907,  p.  353.  The  Heating  and  Ventilation  of  Machine  Shops, 
C.  L.  Hubbard,  Sept.  1907,  p.  1.  Heating  and  Ventilating 
Offices  in  Shops  and  Factories,  C.  L.  Hubbard,  Feb.  1910,  p. 
437.  Pans,  Machinery's  Reference  Series,  No.  39.  The  Heat- 
ing and  Ventilating  Magazine.  Figuring  Flow  of  Air  in  Metal 
Pipes  by  Chart,  B.  S.  Harrison,  Dec.  1905,  p.  1.  Flow  of  Air 
in  Metal  Pipes,  J.  H.  Kinealy,  July  1905,  p.  3.  Friction  of 
Bends  in  Air  Pipes,  J.  H.  Kinealy,  Sept.  1905,  p.  1.  A  Test  of 
Hot  Blast  Heating  Coils,  March  1905,  p.  1.  Simplifying  the 
Installation  and  Operation  of  School  Heating  and  Ventilating 
Apparatus,  S.  R.  Lewis,  July  1908,  p.  10.  A  Rational  For- 
mula Covering  the  Performance  of  Indirect  Heating  Surface, 
Perry  West,  March  1909,  p.  1.  Charts  Showing  the  Perform- 
ance of  Hot  Blast  Coils,  B.  S.  Harrison,  Oct.  1907,  p.  23.  The 
Engineering  Magazine.  Modern  Systems  for  the  Ventilation  and 
Tempering  of  Buildings,  Percival  R.  Moses,  Feb.  1908.  Do- 
mestic Engineering.  Practical  Suggestions  about  Blower  Systems 
for  Shop  Heating,  P.  R.  Still,  Vol.  46,  No.  4,  Jan.  23,  1909  p. 
100;  Vol.  46,  Jan.  30,  1909,  p.  125.  Trans.  A.  S.  H.  &  V.  E. 
Supplementing  Direct  Radiation  by  Fans,  Vol.  X,  p.  286. 
Methods  of  Testing  Blowing  Fans,  R.  C.  Carpenter,  Vol.  VI. 
p.  69.  Some  Experiments  with  the  Centrifugal  Fan,  W.  S. 
Monroe,  Vol.  V,  p.  117. 


CHAPTER  XII. 


MECHANICAL    VACUUM,    STEAM    HEATING    SYSTEMS. 


127.  In  Addition  to  the  Brief  Discussion  of  vacuum  steam 
heating  as  found  in  Arts.  66  and  67,  it  will  be  well  to  discuss 
more  in  detail  the  various  systems  by  which  this  heating  is 
accomplished.  The  advantages  to  be  derived  by  the  positive 
withdrawal  of  the  air  and  the  condensation  from  the  radi- 
ators and  pipes,  compared  to  the  natural  circulation  of  the 
gravity  system,  are  now  too  well  established  to  need  much 
discussion.  Mains  and  returns  that  are  too  small,  horizontal 
runs  of  piping  that  are  unevenly  laid  so  as  to  form  air  and 
water  pockets,  radiators  that  are  only  partially  heated  be- 
cause of  the  entrapped  air,  leaking  air  and  radiator  valves, 
radiators  partially  filled  with  condensation  and  all  the  accom- 
panying cracking  and  pounding  throughout  many  of  the  grav- 
ity systems,  are  sufficient  causes  for  the  general  public  to 
demand  a  cure,  if  such  cure  can  be  found.  One  should  not 
understand  by  this  statement  that  every  mechanical  vacuum 
system  is  a  cure  for  all  the  ills  in  the  heating  work,  for  even 
these  systems  may  be  improperly  designed.  The  steam  pipes 
may  be  too  small  to  supply  the  radiators,  although  smaller 
pipes  may  be  used  in  this  than  in  the  gravity  work,  the 
valves  may  be  defective,  or  the  vacuum  specialties  may  be 
inefficient.  Most  of  the  defects  in  the  average  plant,  however, 
are  because  of  imperfections  in  that  part  of  the  system 
from  the  radiator  to  the  boiler,  and  all  of  the  first  class 
vacuum  systems  are  planned  to  meet  just  these  conditions. 

Vacuum  systems  have  other  advantages  over  the  gravity 
work,  the  principal  one  being  that  of  lifting  the  return  con- 
densation to  a  higher  level.  This  is  noticeable  in  the  plac- 
ing of  radiators  or  coils  in  basement  rooms.  Another  very 
important  advantage  is  in  the  laying  out  of  the  heating  coils 
for.  shop  buildings  and  manufacturing  plants.  Low  pres- 
sure gravity  coils  are  limited  to  a  length  of  about  75  feet. 


170 


HEATING  AND  VENTILATION 


Usually  the  condensation  in  a  long  coil  of  this  kind  is  very 
great  and  requires  extra  heavy  pressure  on  the  steam  end 
to  circulate  it.  The  steam  follows  the  line  of  least  resistance 
and  forces  the  air  out  of  certain  pipes  and  permits  it  to  re- 
main in  others,  the  differential  pressure  not  being  great 
enough  to  eliminate  all  the  air  and  heat  the  pipes  uniformly. 
As  a  result  of  these  conditions  some  of  the  pipes  remain  cold 
and  ineffective  as  prime  radiating  surface.  A  vacuum  sys- 
tem, with  its  positive  circulation,  increases  the  differential 
pressure,  removes  the  air  and  gives  uniform  heating  effect  in 
coils  that  are  several  times  as  long  as  can 'be  safely  supplied 
by  the  gravity  system.  The  accumulation  of  air  in  the  radi- 
ators and  coils  is  especially  noticeable  in  systems  vising  ex- 
haust steam. 

When  exhaust  steam  from  engines  or  turbines  is  used 
in  a  gravity  heating  system,  the  back  pressure  is  carried 
from  atmospheric  pressure  to  10  pounds  gage.  With  the  ap- 
plication of  the  vacuum  system  it  is  possible  to  maintain  this 
constantly  at  about  atmospheric  pressure.  It  is  claimed  by 
some,  that  it  is  possible  to  reduce  the  pressure  in  the  radiators 
to  such  a  degree  that  the  pressure  in  the  supply  mains  will 
fall  considerably  below  atmosphere.  No  doubt  the  specialty 


Fig.    77. 


MECHANICAL,  VACUUM   HEATING  171 

valves  may  be  set  so  as  to  do  this,  but  it  would  scarcely  be 
considered  an  economical  arrangement. 

The  principal  features  of  a  mechanical  vacuum  system 
are  shown  in  Fig.  77.  Live  steam  is  conducted  to  the  engine 
and  to  the  heating  main,  the  latter  through  a  pressure  re- 
ducing valve  to  be  used  only  when  exhaust  steam  is  insuf- 
ficient. The  exhaust  steam  from  the  engines  and  pumps 
is  conducted  to  the  heating  main  and  to  the  feed  water 
heater.  The  exhaust  steam  line  opens  to  the  atmosphere 
through  a  back  pressure  valve  which  is  set  at  the  desired 
pressure  for  the  supply  steam.  An  oil  separator  shown  on  the 
exhaust  steam  line  removes  the  oil  and  delivers  it  to  an  oil 
trap.  At  the  entrance  to  the  feed  water  heater,  the  exhaust 
steam  passes  through  a  series  of  baffle  plates  which  remove 
the  oil  and  entrained  water  from  that  part  of  the  steam  which 
enters  the  heater.  A  boiler  feed  pump  and  a  vacuum  pump, 
with  the  attending  valves  and  governing  appliances,  com- 
plete the  power  room  equipment.  The  steam  supply  to  the 
heating  system  is  piped  to  radiators  and  coils  in  the  ordinary 
way,  with  or  without  temperature  control.  A  thermostatic 
valve,  or  patented  motor  valve,  is  placed  at  the  return  end  of 
each  radiator  and  coil  and  these  returns  are  then  brought  to- 
gether in  a  common  return  which  leads  to  a  vacuum  pump  or 
ejector.  The  return  pipe  and  specialty  valve  for  any  one 
unit  is  usually  y2  inch.  The  combined  return  increases  in 
size  as  more  radiation  is  taken  on.  Horizontal  steam  mains 
usually  terminate  in  a  drop  leg  which  is  tapped  to  the  return 
8  to  15  inches  above  the  bottom  of  the  leg.  Each  rise  in  the 
system  has  a  drop  leg  at  the  lower  end  of  the  rise.  These 
points  and  all  other  points  where  condensation  may  collect 
are  drained  through  specialty  valves  to  the  return.  Water 
supply  systems  may  be  tapped  for  steam  and  return  con- 
densation the  same  as  any  ordinary  radiator.  Steam  is 
carried  in  the  main  at  about  atmospheric  pressure,  and  just 
enough  vacuum  is  maintained  on  the  return  to  insure  positive 
and  noiseless  circulation.  In  many  cases  where  special  lifts 
are  required,  these  return  systems  are  run  under  a  negative 
pressure  of  6  to  10  inches  of  mercury.  Under  such  con- 
ditions water  may  be  lifted  from  6  to  10  feet.  Either  closed 
or  opened  feed  water  heaters  may  be  used  with  the  layout 
as  given. 

Fig.  78  shows  a  section  through  the  Marsh  vacuum  pump 
which  represents  a  type  very  generally  used  in  this  work. 


172 


HEATING  AND  VENTILATION 


It  will  be  noticed  that  this  pump  has  a  steam  operated  valve. 
The  automatic  governing  feature  of  this  valve  tends  to  equal- 
ize the  cylinder  pres- 
sure to  meet  the  vary- 
ing resistance  in  the 
main  return  of  the 
heating  system.  Such 
a  pump  is  handling 
alternately  solid  wa- 
ter and  vapors,  hence 
there  is  great  ten- 
dency of  the  ordinary 
pump  to  race  and 
pound  at  such  times. 
In  its  operation  the 
steam  enters  at  A  and 
passes  into  the  space 
B  through  the  annu- 
lar opening  C  be- 
Fig.  78.  tween  the  reduced 

neck  of  the  valve  and 

the  bore  of  the  first  chest  wall.  It  is  thus  projected  against 
the  inside  surface  of  the  valve  head  before  entering  into 
the  port  and  passing  to  the  cylinder.  On  reaching  the 
cylinder  and  driving  the  piston  to  the  right,  the  reaction  of 
the  steam  through  port  D  to  the  opposite  side  of  the  valve 
head,  tends  to  further  open  the  steam  port  G.  The  valve 
then  holds  a  position  depending  upon  the  relative  strength 
of  the  forces  which  tend  to  move  it  in  opposite  directions, 
i.  e.,  admission  steam  which  tends  to  close  the  valve,  and  the 
cylinder  steam  which  tends  to  open  the  valve.  This 
is  the  governing  feature.  It  will  be  noticed  that  the  pump 
piston  is  in  two  parts  and  carries  steam  at  admission  pres- 
sure upon  the  inside.  This  steam  is  admitted  along  the 
dotted  line  to  the  center  of  the  cylinder  head,  thence  through 
a  small  tube  and  packing  box  to  the  hollow  piston  rod,  which 
has  a  direct  connection  with  the  center  of  the  piston.  When 
the  piston  has  moved  sufficiently  to  bring  the  central  space 
E  in  line  with  the  duct  D,  steam  is  admitted  to  the  right  of 
the  piston  valve  thus  forcing  it  back,  cutting  off  the  steam  at 
C,  opening  up  the  exhaust  to  the  atmosphere  through  F  and 
admitting  steam  to  the  other  end  of  the  cylinder.  The  action 
is  thus  reversed  and  continuous.  Ejectors  operated  by  steam, 


MECHANICAL  VACUUM   HEATING 


173 


water  and  electricity  are  also  used  to  produce  a  vacuum. 
No  comparison  is  made  here  of  the  various  systems  of  pro- 
ducing vacuum  since  each  gives  satisfaction  when  properly 
installed.  In  each  case  there  is  a  loss  of  energy  but  this 
loss  is  amply  repaid  in  the  added  benefits. 

Several  patented  systems  of  mechanical  vacuum  heating 
are  now  upon  the  market.  These  are  in  large  measure  an 
outgrowth  of  the  original  Williames  System,  patented  in 
1882.  Each  system  is  well  represented  by  the  above  diagram 
in  all  particulars  concerning  the  steam  and  water  circu- 
lation. The  chief  difference  between  them  is  in  the  thermo- 
static  or  motor  connection  at  the  entrance  to  each  individual 
return. 

128.  Webster  System: — In  this  system  a  pump  is  used  to 
produce  the  vacuum.  A  special  fitting,  called  a  water-seal 
motor,  is  used  on  all  radiators,  coils  and  drainage  points. 
Fig.  79  shows  a  section  of  one  of  the  valves.  Other  models 
are  constructed  so  as  to  have  the  outlet  in  a  horizontal  di- 
rection, either  parallel  with  or  90  degrees  to  the  inlet.  Jig. 
80  shows  an  application  of  this  to  a  radiator  or  coil.  The 
dirt  strainer  is  usually  placed  between  the  radiator  or  coil  and 


^HL— C 


Fig.   80. 


the  motor  valve.  This  strainer  collects  the  dirt  and  pro- 
tects from  clogging  the  motor  valve.  C  attaches  to  the  re- 
turn end  of  the  radiator  or  coil  and  L  leads  to  the  vacuum 
pump.  O  is  the  central  tube,  the  lower  end  of  which  is  a 
valve.  A  is  a  hollow  cylindrical  copper  float,  the  central  tube 


174 


HEATING  AND  VENTILATION 


of  which  fits  loosely  over  spindle  B.  The  function  of  the 
cylinder  A  is  to  raise  the  tube  G  from  the  seat  H  and  open 
the  discharge  to  the  pump.  Ordinarily,  the  float  is  down  and 
the  central  tube  valve  is  resting-  upon  the  seat  and  cuts  off 
communication  with  the  radiator,  excepting  as  air  may 
be  drawn  from  the  radiator  down  the  central  tube 
around  the  spiral  plug.  The  water  of  condensation  accumu- 
lating in  the  radiator  or  coil  passes  into  the  chamber  E, 
sealing  the  valve,  and  when  sufficient  water  has  accumulated 
to  lift  the  float,  it  opens  a  passageway  for  a  certain  amount 
of  the  water  to  be  withdrawn  to  the  return.  When  this 
water  becomes  lowered  sufficiently,  the  valve  again  seats 
itself  and  the  cycle  is  completed.  This  action  continues  as 
long  as  water  is  present  in  the  radiator.  These  motor  valves 
are  made  of  three  sizes,  y2  inch,  %  inch  and  1  inch.  The 
first  is  the  standard  size  and  has  a  capacity  of  approximately 
200  feet  of  radiation. 

Fig.   81   shows  a  ther  mo  static  valve  for  many  years  in  use 
by   this   Company   and   lately   replaced   by   the    above   motor 
valve.      It   will   be   seen   that  the   automatic   feature    in   this 
valve    is    the    compound    rubber    stalk, 
which  expands  and  contracts  under  heat 
and  cold.      The  adjusting  screw  at  the 
top  permits  the  valve  to  be  set  for  any 
conditions  of  temperature  and  pressure 
within     the     radiator.       The     water     of 
condensation    passes    through    a    screen 
and    surrounds   the    rubber    stalk.      The 
temperature    of    the    water    being    less 
than  that  of  steam,  the  stalk  contracts 
and    the    water    is    drawn    through    the 
opening  A   by   the   action   of  the   pump. 
As  soon  as  the  water  has  been  removed, 
steam   flows   around   the   stalk  and   ex- 
pands it  until  it  closes  the  seat.     This 
process    is    a    continuous    one    and    auto- 
matically removes  the  water  from  the  radiator.     The  screen 
serves  the  purpose  of  the  dirt  strainer  as  mentioned  above. 
A  suction  strainer,  which  is  very  similar  to  the  dirt  strainer 
only  larger  in  capacity,  is  placed  upon  the  return  line  next 
the  pump.     This  fitting  usually  has  a  cold  water  connection 
to  be   used  at  times  to   assist   in  producing  a  more   perfect 


Fig.   81. 


OF 

£A  LI  FOB? 

]CHANICAL  VACUUM  HEATING 


175 


vacuum.  The  piping  system  for  the  automatic  control  of 
the  vacuum  pump  is  shown  in  Fig.  82.  It  will  be  seen  that 
the  vacuum  in  the  return  operates 
through  the  governor  to  regu- 
late the  steam  supply  to  the 
pump  cylinder,  thus  controlling 
the  speed  of  the  pump. 

Occasionally  it  is  desirable  to 
have  certain  parts  of  the  heating 
system  under  a  different  vacuum. 
An  illustration  of  this  would  be, 
where  the  radiators  within  the 
building  were  run  under  a  neg- 
ative pressure  of  about  one 
pound,  and  a  set  of  heating  coils 


Fig.   82. 


in  the  basement  were  to  be  carried  under  a  negative  pressure 

of  four  pounds.  The  Web- 
ster iSystem,  type  D,  Fig. 
83,  meets  this  condition. 
The  exact  difference  be- 
tween the  suction  pressure 
and  the  pressure  in  the 
radiators  can  be  varied  to 
suit  any  condition  by  the 
controller  valve.  A  trap 
and  a  controller  valve 
should  be  applied  to  each 
line  having  a  different 
pressure  from  that  in  the  suction  line. 

A  modulation  valve,  for  graduating  the  steam  supply  to  the 
radiator,  has  been  designed  by  this  Company  and  may 
be  applied  to  any  Webster  Heating  System  to  assist  in  its 
regulation.  This  modulation  valve  serves  to  graduate  the 
steam  supply  to  the  radiators  so  that  the  pressure  may  be 
maintained  at  any  point  to  suit  the  required  heat  loss  from  the 
building. 

129.  VamAuken  System: — In  this  system,  as  in  the  pre- 
vious one,  the  vacuum  in  the  return  main  is  produced  by  a 
vacuum  pump  which  is  controlled  by  an  especially  designed 
governor.  The  automatic  valves  which  are  placed  on  the 
radiators,  coils  and  other  drainage  points  along  the  system, 
are  called  Belvac  Thermoflres,  and  are  shown  in  section  by 
Fig.  84.  This  valve  is  automatic  and  removes  the  water  of 


176 


HEATING  AND  VENTILATION 


Fig-.   84. 


condensation  by  the  controlling  ac- 
tion of  a  float.  It  is  connected  to  the 
radiator  or  coil  at  K  and  to  the  vacu- 
um return  pipe  at  L.  The  water  of 
condensation  is  drawn  through  the 
return  pipe  into  chamber  D  until  it 
reaches  the  inverted  weir  E  which 
gives  it  a  water  seal.  It  is  thence 
drawn  upward  into  space  D  until  it 
overflows  into  the  float  chamber  AA, 
where  it  accumulates  until  the  line 
of  flotation  is  reached.  When  the 
float  C  lifts,  the  valve  seat  at  B  opens 
and  allows  the  water  'to  escape  into 
the  vacuum  return  pipe.  After  the 
removal  of  the  w^ater  the  float  again  settles  on  seat  B  until 
sufficient  water  accumulates  in  the  float  chamber  to  again 
lift  it,  when  the  cycle  is  repeated. 

The  air  contained  in  the  radiators  or  coils  is  drawn 
through  the  return  and  up  through  chamber  D  into  the  top  of 
the  float  chamber.  Here  its  direction  follows  arrows  GO, 
being  drawn  through  the  small  opening  in  the  guide-pin  at 
F,  down  through  the  hollow  body  of  the  copper  float  and 
valve  seat  B,  into  the  vacuum  return.  This  removal  of  air  is 
continuous  regardless  of  the  amount  of  water  present.  The 
by-pass  /,  when  open,  allows  all  dirt,  coarse  sand  or  scale 
to  pass  directly  into  the  vacuum  return,  thus  cleaning  the 
valve.  By  opening  the  by-pass  /,  only  part  way,  the  con- 
tents of  chamber  A  may  be  emptied  into  the  vacuum  return 
without  interfering  with  the  conditions  in  space  D.  The 
ends  of  the  float  are  symmetrical,  hence  it  will  work  either 
way.  The  thermofires  are  made  in  four  standard  sizes  of 
outlets,  two  having  y2  inch  and  two  having  %  inch  outlets. 
These  valves  have  capacities  of  125,  300,  550  and  1200  square 
feet  of  radiation  respectively. 

Drop  legs,  strainers,  governors  and  other  specialties 
usually  provided  by  such  comipanies  are  supplied  in  addition 
to  the  thermofires.  When  a  differential  vacuum  is  to  be  ob- 
tained a  special  arrangement  of  the  piping  system  is  planned 
to  cover  this  point.  The  piping  connections  around  the  auto- 
matic pump  governor  are  the  same  as  are  shown  in  Fig.  82. 


MECHANICAL  VACUUM   HEATING 


177 


130.  Automatic  Vacuum  System: — In  this  system  the 
automatic  vacuum  valve,  which  takes  the  place  of  the  motor  valve 
and  thermofire  in  the  two  preceding  systems,  is  shown  in 
Pig.  85.  K  is  the  entrance  to  the  radiator  and  L  to  the 

vacuum  return.  Screen  V 
prevents  scale  and  dirt 
from  entering  the  valve. 
By-pass  E  is  for  emerg- 
\K  ency  use  in  draining  off 
accumulated  water  and 
dirt,  should  the  valve  clog. 
With  such  an  adjust- 
ment the  bonnet  of  the 
valve  may  be  removed 
for  inspection  without 
overflowing.  Before  the 
steam  is  turned  on  in  the 

radiator  the  float  is  tipped,  as  shown  in  the  figure,  making 
a  small  wedge  shaped  opening  through  which  the  vacuum 
can  pull  on  the  radiator.  When  steam  is  admitted  to  the  radi- 
ator, condensation  flows  into  the  valve,  lifting  the  float  and 
sealing  the  outlet  against  the  passage  of  steam.  As  the  valve 
continues  to  fill  with  water  the  float  is  lifted,  and  water 
passes  to  the  vacuum  return.  As  the  water  is  drawn  off  the 
float  falls  and  reseats  on  the  nipple  when  about  y2  inch  of 

water  remains  in  the  valve, 
thus  maintaining  the  water 
seal.  Fig.  86  shows  the 
piping  connections  around 
the  automatic  pump  gov- 
ernor. It  will  be  seen  that 
this  connection  differs  from 
that  of  the  Webster  and 
Van  Auken  Systems,  in  that 
the  pressure  in  the  return 
main  controls  the  flow  of 
injection  water  into  the 


Fig. 
suction  strainer. 


131.  Paul  System: — Referring  to  Art.  67  it  will  be  seen 
that  the  Paul  System  is  essentially  a  one-pipe  system,  with  the 
vacuum  principle  attached  to  the  air  valve.  Its  use  is  not 
restricted  to  the  one-pipe  radiator,  since  it  may  be  applied 


178 


HEATING  AND  VENTILATION 


to  the  two-pipe  radiator  as  well.  The  advantage  to  be  gained, 
however,  when  applied  to  the  former,  is  much  greater  than 
in  the  latter  because  of  the  greater  possibility  of  air  clog- 
ging the  one-pipe  radiator.  This  one  fact  has  largely  deter- 
mined its  field  of  operation.  This  system  differs  from  the 
ones  just  mentioned  in  two  essential  points;  first,  the  vacu- 
um effect  is  applied  at  the  air  valve  and  the  water  of  con- 
densation is  not  moved  by  this  means;  second,  the  vacuum 
effect  is  produced  by  the  aspirator  principle  using  water, 
steam  or  compressed  air,  as  against  the  pumps  used  by  the 
other  companies.  The  same  principle  may  also  be  applied  to 
the  tank  receiving  the  condensation.  By  this  means  it  is 
possible  to  remove  all  the  air  in  the  system  and  to  produce 
a  partial  vacuum  if  necessary.  Ordinarily  the  vacuum  is 
supposed  to  extend  only  as  far  as  the  air  valve  at  the  radi- 
ator. If  desired,  however,  this  valve  may  be  adjusted  so 
that  the  vacuum  effect  may  be  felt  within  the  radiator,  and 
in  some  cases  mlay  extend  into  the  supply  main.  Many 
modifications  of  the  Paul  System  are  being  used.  In  its  la- 
test development,  the  layout  of  the  system  for  large  plants,  is 


Fig-.  87. 


MECHANICAL  VACUUM  HEATING  179 

about  the  same  as  that  shown  in  Fig  77,  where  all  of  the 
principal  pieces  of  apparatus  that  go  to  make  up  the  power 
room  equipment  are  present.  Fig.  87  shows  a  typical  vacuum 
connection  between  one-pipe  and  two-pipe  radiators  and  the 
exhauster.  This  diagram  shows  the  discharge  leading  to  a 
tank,  sewer  or  catch  basin.  If  exhaust  steam  were  used,  the 
discharge  would  probably  lead  into  the  steam  supply  to  one 
or  more  of  the  radiators  and  then  into  the  atmosphere. 
Where  electric  current  can  be  had  this  exhausting  may  be 
done  by  the  use  of  an  electric  motor.  A  specially  designed 
thermostatic  air  valve  is  supplied  by  the  Company  to  be 
used  on  this  system. 

Other  vacuum  systems,  each  having  a  full  line  of  specialty 
appliances,  might  be  mentioned  here  but  the  above  are  con- 
sidered sufficient. 


180  HEATING  AND  VENTILATION 


REFERENCES. 

References    on    Mechanical    Vacuum    Heating. 

TECHNICAL  BOOKS. 

Snow,  Principles  of  Heat.,  Chap.  XL.  Carpenter,  Heating  <& 
Vent.  Blags.,  p.  285.  Hubbard,  Power,  Heat.  &  Ventilation,  p.  568. 
TECHNICAL  PERIODICALS. 

Engineering  Review.  Steam  Heating  Installation  in  the 
Biology  and  Geology  Building1  and  the  Vivarium  Building, 
Princeton  University  (Webster  System),  Jan.  1910,  p.  27. 
Steam  Heating  and  Ventilating  Plant  Required  for  Addition 
to  Hotel  Astor  (Paul  System),  March  1910,  p.  27.  Heating 
Four  Store  Buildings  at  Salina,  Kan.,  (Moline  System,  vacuum 
vapor),  April  1910,  p.  45.  Steam  Heating  System  for  Henry 
Doherty's  Mill,  Paterson,  N.  J.,  May  1910,  p.  37.  Heating 
Residences  at  Fairfield,  Conn.,  (Bremen's  System  of  Vapor 
Heating),  June  1910,  p.  52.  Heating  Residence  at  Fleming- 
ton,  N.  J.,  (Vapor- Vacuum  System),  July  1910,  p.  43.  Heating 
System  installed  in  the  Haynes  Office  Building,  Boston,  (Web- 
ster Modulation  System),  Aug.  1910,  p.  44.  Heating  the 
Silversmith's  Building,  New  York,  (Thermograde  System), 
Jan.  1908,  p.  8.  Heating  System  in  the  New  Factory  of  Jen- 
kins'  Bros.,  Ltd.,  Montreal,  Canada  (Positive  Differential 
System),  Dec.  1907,  p.  14.  The  Railway  Review.  Vacuum  Ventila- 
tion for  Street  Cars,  Oct.  23,  1909,  p.  948. 


CHAPTER  XIII. 


DISTRICT     HEATING     OR     CENTRALIZED     HOT     WATER 
AND   STEAM  HEATING. 


GENERAL. 

132.  Heating  Residences  and  Business  Blocks  from  a  cen- 
tral station  is  a  method  that  is  being  employed  in  many  cities 
and   towns   throughout   the   country.      The   centralization   of 
the   heat  supply   for  any   district   in  one   large   unit   has  an 
advantage  over  a  number  of  smaller  units  in  being  able  to 
burn  the  fuel  more  economically,   and  in  being  able  to   re- 
duce labor  costs.     It  has  also  the  advantage,  when  in  con- 
nection  with   any   power    plant,    of    saving   the    heat   which 
would  otherwise  go  to  waste  in  the  exhaust  steam  and  stack 
gases,    by   turning    it   into   the    heating   system.      The    many 
electric  lighting  and  pumping  stations  around  the  country 
give   large    opportunity   in   this   regard.      Since   the   average 
steam  power  plant  is  very  wasteful  in  these  two  particulars, 
any  saving  that  might  be  brought  about  should  certainly  be 
sought   for.     On   the   other   hand,    however,    a   plant   of   this 
kind  has  the  disadvantage  in  that  it  necessitates  transmitting 
the   heating   medium   through   a   system   of   conduits,    which 
generally  is  a  wasteful  process.     The  failure  of  many  of  the 
pioneer  plants  has  cast  suspicion  upon  all  such  enterprises 
as  paying  investments,  but  the  successful  operation  of  many 
others   shows   the   possibilities,    where   care    is    exercised    in 
their  design  and  operation. 

133.  Important  Considerations  in  Central  Station  Heat- 
Ing: — In  any  central  heating  system,  the  following  consider- 
ations will  go  far  towards  the  success  or  the"  failure  of  the 
enterprise: 

First. — There  should  be  a  demand  for  the  heat. 
Second. — The  plant  should  be  near  to  the  territory  heated. 
Third. — There  should  be  good  coal  and  water  facilities  at 
the  plant. 


182  HEATING  AND  VENTILATION 

Fourth. — The  quality  of  all  the  materials  and  the  instal- 
lation of  the  same,  especially  in  the  conduit  concerning  in- 
sulation, expansion  and  contraction,  and  durability,  are 
points  of  unusual  importance. 

Fifth. — The  plant  must  be  operated  upon  an  economical 
basis,  the  same  as  is  true  of  other  plants. 

Sixth. — The  load-factor  of  the  plant  should  be  high.  This 
is  one  of  the  most  important  points  to  be  considered  in  com- 
bined heating  and  power  work.  The  greater  the  proportion 
of  hours  each  piece  of  apparatus  is  in  operation,  to  the  total 
number  of  hours  that  the  plant  is  run,  the  greater  the  plani. 
efficiency.  The  ideal  load-factor  is  where  all  of  the  apparatus 
is  running  at  full  load  all  the  time. 

The  average  conduit  radiates  a  great  deal  of  heat,  hence, 
the  nearer  the  plant  to  the  heated  district  the  greater  the 
economy  of  the  system.  Likewise  a  location  near  a  railroad 
minimizes  fuel  costs;  and  good  water,  with  the  possibility 
of  saving  the  water  of  condensation  from  the  steam;  all  serve 
to  the  increased  economy  of  the  plant.  It  is  to  be  expected 
that  even  a  well  designed  plant,  unless  safeguarded  against 
ills  as  above  suggested,  would  soon  succumb  to  inevitable 
failure. 

Two  types  of  centralized  heating  plants  are  in  use,  hot 
water  and  steam.  Each  will  be  discussed  separately.  In  the 
discussion  of  either  system,  certain  definite  conditions  will 
have  to  be  met.  First  of  all,  there  should  be  a  demand  in 
that  certain  locality  for  such  a  heating  system,  before  the 
plant  can  be  considered  a  safe  investment.  To  create  a  de- 
mand requires  good  representatives  and  a  first  class  resi- 
dence or  business  district.  When  this  demand  is  obtained 
the  plan  of  the  probable  district  to  be  heated  will  first  be 
platted  and  then  the  heating  plant  will  be  located.  In  many 
cases  the  heating  plant  will  be  an  added  feature  to  an  al- 
ready established  lighting  or  power  plant  and  its  location 
will  be  more  or  less  a  predetermined  thing1. 

In  addition  to  these  material  and  financial  features  just 
mentioned,  one  must  consider  the  legal  phases  that  always 
come  up  at  such  a  time.  These  relate  chiefly  to  the  franchise 
requirements  that  must  be  met  before  occupying  the  streets 
with  conduit  lines,  etc.  All  of  these  considerations  are  a 
part  of  the  one  general  scheme. 


DISTRICT  HEATING  183 

134.     The  Scope  of  the  \Vork  in  Central  Station  Heating 
may  be  had   from  the  following  outline: 


{  Exhaust  Steam  Heaters 
Live  Steam  Heaters 


CENTRAL    STA- 


Hot  Water  Heating 


Heating  Boilers 


by  use  of. 

I  Economizers 

Injectors  or 


TION  HEATING 

Co-Mingle  rs 


Exhaust  Steam 
.  Steam  Heating. 

Live  Steam 


In  the  hot  water  system  the  return  water  at  a  lowered  tem- 
perature enters  the  power  plant,  is  passed  through  one  or 
more  pieces  of  apparatus  carrying  live  or  exhaust  steam,  or 
flue  gases,  and  is  raised  in  temperature  again  to  that  in  the 
outgoing  main.  From  the  above,  a  number  of  combinations 
of  reheating  can  be  had.  Any  or  all  of  the  units  may  be  put 
in  one  plant  and  the  piping  system  so  installed  that  the  water 
will  pass  through  any  single  unit  and  out  into  the  main;  or, 
the  water  may  be  split  and  passed  through  the  units  in  par- 
allel; or,  it  may  be  made  to  pass  through  the  units  in  series. 
All  of  these  combinations  are  possible,  but  not  practicable. 
In  most  plants,  two  or  three  combinations  only  are  provided. 
In  the  existing  plants  the  order  of  preference  seems  to  be, 
exhaust  steam  reheaters,  economizers,  heating  boilers,  inject- 
ors or  co-minglers,  and  live  steam  heaters. 

All  of  the  above  pieces  of  reheating  apparatus  operate 
by  the  transmission  of  heat  through  metal  surfaces,  such  as 
brass,  steel  or  cast  iron  tubes,  excepting  the  co-mingler,  this 
being  simply  a  barometric  condenser  in  which  the  exhaust 
steam  is  condensed  by  the  injection  water  from  the  return 
main,  the  mixture  being  drawn  directly  into  the  pumps. 

The  objection  to  the  tube  transmission  is  the  lime,  mud 
and  oil  deposit  on  the  tube  surfaces,  thus  reducing  the  rate 
of  transmission  and  requiring  frequent  cleaning.  The  ob- 
jections to  the  co-minglers  are,  first,  that  the  pumjp  must 
draw  hot  water  from  the  condenser  and  second,  that  a  certain 
amount  of  the  oil  passes  into  the  heating  line.  With  per- 


184  HEATING  AND  VENTILATION 

fected  apparatus  for  removing  the  oil,  the  co-mingler  will 
no  doubt  supersede,  to  a  large  degree,  the  tube  reheaters  in 
hot  water  heating. 

In  the  steam  system  the  proposition  is  very  much  simplified. 
The  exhaust  steam  passes  through  one  or  more  oil  separating 
devices  and  is  then  piped  directly  to  the  header  leading 
to  the  outgoing  main.  Occasionally  a  connection  is  made  from 
tuis  line  to  a  condenser,  such  that  the  steam,  when  not  used 
in  the  heating  system,  may  be  run  directly  to  the  condenser. 
These  pipe  lines,  of  course,  are  all  properly  valved  so  that  the 
current  of  steam  may  easily  be  deflected  one  way  or  the 
other.  In  addition  to  this  exhaust  steam  supply,  live  steam 
is  provided  from  the  boiler  and  enters  the  header  through 
a  pressure  reducing  valve.  In  any  case  when  the  exhaust 
steam  is  insufficient  the  supply  may  be  kept  constant  by  auto- 
matic regulation  on  the  reducing  valve. 

In  selecting  between  hot  water  and  steam  systems  the 
preference  of  the  engineer  is  very  largely  the  controlling 
factor.  The  preference  of  the  engineer,  however,  should  be 
formed  from  facts  and  conditions  surrounding  the  plant,  and 
should  not  come  from  mere  prejudice.  The  following  points 
are  some  of  the  important  ones  to  be  considered: 

First  cost  of  plant  installed. — This  is  very  much  in  favor  of 
the  steam  system  in  all  features  of  the  power  plant  equip- 
ment, the  relative  costs  of  the  conduit  and  the  outside  work 
being  very  much  the  same. 

Cost  of  operation. — This  is  in  favor  of  the  hot  water  sys- 
tem because  of  the  fact  that  the  steam  from  the  engines 
may  be  condensed  at  or  below  atmospheric  pressure,  while 
the  exhausts  from  the  engines  in  the  steam  systems  must 
be  carried  from  five  to  fifteen  pounds  gage,  which  naturally 
throws  a  heavy  back  pressure  upon  the  engine  piston. 

Pressure  in  circulating  mains. — This  is  in  favor  of  the  steam 
system.  The  pressure  in  any  steam  radiator  will  be  only 
a  few  pounds  above  atmosphere,  while  in  a  hot  water  sys- 
tem, connected  to  high  buildings,  the  pressure  on  the  first 
floor  radiators  near  the  level  of  the  mains,  becomes  very 
excessive.  The  elevation  of  the  highest  radiator  in  the 
circuit,  therefore,  is  one  of  the  determining  factors. 

Regulation. — It  is  easier  to  regulate  the  hot  water  system 
without  the  use  of  the  automatic  thermostatic  control,  since 
the  temperature  of  the  water  is  maintained  according  to  a 


DISTRICT  HEATING  185 

schedule,  which  fits  all  degrees  of  outside  temperature.  When 
automatic  control  is  applied,  this  advantage  is  not  so  marked. 

Returning  the  icater  to  the  power  plant. — In  most  steam  plants 
the  water  of  condensation  is  passed  through  indirect  heaters, 
to  remove  as  much  of  the  remaining  heat  as  possible  and 
is  then  run  to  the  sewer.  This  procedure  incurs  a  consider- 
able loss,  especially  in  cold  weather  when  the  feed  water 
at  the  power  plant  is  heated  from  low  temperatures.  This 
point  is  in  favor  of  the  hot  water  system. 

Estimating  charges  for  heat. — This  is  in  favor  of  the  steam 
system  since,  by  meter  measurement,  a  company  is  able  to 
apportion  the  charges  intelligently.  The  flat  rate  charged  for 
water  heating  and  for  some  steam  heating  is  in  many  cases 
a  decided  loss  to  the  company. 

135.  Conduits: — In  installing  conduits  for  either  hot 
water  or  steam  systems  the  selection  should  be  made  after 
determining,  first,  its  efficiency  as  a  heat  insulator;  second, 
its  initial  cost;  third,  its  durability.  Other  points  that  must 
be  accounted  for  as  being  very  essential  are:  the  supporting, 
anchoring,  grading  and  draining  of  the  mains;  provision  for 
expansion  and  contraction  of  the  mains;  arrangements  for 
taking  off  service  lines  at  points  where  there  is  little  move- 
ment of  the  mains;  and  the  draining  of  the  conduit. 

Some  conduits  may  be  installed  at  very  little  cost  and 
yet  may  be  very  expensive  propositions,  because  of  their  in- 
ability to  protect  from  heat  losses;  while,  on  the  other  hand, 
some  of  the  most  expensive  installations  save  their  first 
cost  in  a  couple  of  years'  service.  Many  different  kinds  of 
insulating  materials  are  used  in  conduit  work  such  as  mag- 
nesia, asbestos,  hair  felt,  wool  felt,  mineral  wool  and  air  cell. 
Each  of  these  materials  has  certain  advantages  and  under  cer- 
tain conditions  would  be  preferred.  It  is  not  the  real  purpose 
here  to  discuss  the  merits  of  the  various  insulators,  because 
the  quality  of  the  workmanship  in  the  conduit  enters  into  the 
final  result  so  largely.  The  different  ways  that  pipes  may 
be  supported  and  insulated  in  outside  service  will  be  given, 
with  general  suggestions  only.  E  ig.  88  shows  a  few 
of  the  many  methods  in  common  use.  A  very  simple  conduit 
is  shown  at  A.  This  is  built  up  of  wood  sections  fitted  end 
to  end,  then  covered  with  tarred  paper  to  prevent  surface 
water  leaking  in  and  bound  with  straps.  The  pipe  either  is  a 


186  HEATING  AND  VENTILATION 

loose  fit  to  the  bore  and  rests  upon  the  inner  surface,  or  is 
supported  on  metal  stools,  driven  into  the  wood  or  merely 
resting  upon  it.  These  stools  hold  the  pipe  concentric  with 
the  inner  bore  of  the  log.  With  much  movement  of  the 
pipe  endwise,  from  expansion  and  contraction,  these  stools 
should  not  be  used  unless  they  are  loose  and  have  a  wide 
surface  contact  with  the  wood.  A  metal  lining  with  the  pipe 
resting  directly  upon  it  is  considered  good.  The  conduit  is 
laid  to  a  good  straight  run  in  a  gravel  bed  and  usually  over 
a  small  tile  drain  to  carry  off  the  surface  water,  excepting 
as  this  drain  is  not  necessary  in  sections  where  there  is  good 
gravel  drainage.  The  insulation  in  A.  is  only  fair.  The  air 
space  around  the  pipe,  however,  is  to  be  commended.  B  is 
an  improvement  over  A  and  is  built  up  of  boards  notched 
at  the  edges  to  fit  together.  The  materials  used,  from  the 
outside  to  the  center,  are  noted  on  the  sketch  beginning 
with  the  top  and  reading  down.  This  covering  is  in  general 
use  and  gives  good  satisfaction  from  every  standpoint.  C 
shows  a  good  insulation  and  supports  the  pipe  upon  rollers 
at  the  center  of  a  line  of  halved,  vitrified  tile.  The  lower 
half  of  the  tile  should  be  graded  and  the  pipe  then  run  upon 
the  rollers,  after  which  it  may  be  covered  with  some  pre- 
pared covering  and  the  remaining  space  next  the  tile  filled 
with  asbestos,  mineral  wool  or  other  like  material.  D  shows 
the  same  adapted  to  cellar  work.  Occasionally  two  pipes  are 
run  side  by  side,  main  and  return,  in  which  case  large  halved 
tiles  may  be  used  as  in  E,  having  large  metal  supports  curved 
on  the  lower  face  to  fit  the  tile.  If  these  supports  are  not 
desired  the  same  kind  of  straight  tiles  may  be  used  with  a 
Tee  tile  inserted  every  8  to  12  feet  having  the  bell  looking 
down  as  in  F.  In  this  bell  is  built  a  concrete  setting  with 
iron  supports  for  the  pipes  which  run  on  rollers,  over  a  rod. 
These  rollers  are  sometimes  pieces  of  pipes  cut  and  reamed, 
but  are  better  if  they  are  cast  with  a  curvature  to  fit  the 
pipes  to  be  supported.  This  form  of  conduit,  when  drained 
to  good  gravel,  gives  first  class  service.  G,  H  and  /  show 
box  conduits  with  two  or  more  thicknesses  of  %  inch  boards 
nailed  together  for  the  sides,  top  and  bottom.  The  bottom 
of  the  conduit  is  first  laid  and  the  pipe  is  run.  The  sides 
are  then  set  in  place  and  the  insulating  material  put  in, 
after  which  the  top  is  set  and  the  whole  filled  in.  7  shows 


DISTRICT  HEATING 


187 


Fig-.  88. 


188  HEATING  AND  VENTILATION 

the  best  form  of  box,  since  with  the  air  spaces  this  is  a 
very  good  insulator.  All  wood  boxes  are  very  temporary, 
hence,  brick  and  concrete  are  usually  preferred.  K  is  a 
conduit  with  8-inch  brick  walls  covered  with  flat  stones  or 
halved  glazed  tiles  cemented  to  place  to  protect  from  sur- 
face leakage.  The  bottom  of  the  conduit  has  supports  built 
in  every  8  to  12  feet,  and  between  these  points  the  conduit 
drains  to  the  gravel.  The  usual  rod  and  roller  here  serve 
as  pipe  supports.  The  pipe  is  covered  with  sectional  cover- 
ing and  the  rest  of  the  space  may  or  may  not  be  filled  with 
wool  or  chips,  as  desired.  L  shows  the  sectional  covering 
omitted  and  the  entire  conduit  filled  with  mineral  wool,  hair 
felt  or  asbestos,  and  ashes.  M  has  the  supporting  rod  built 
into  the  sides  of  the  conduit  and  has  the  bottom  of  the  con- 
duit bricked  across  and  cemented  to  carry  the  leaks  and 
drainage  to  some  distant  point.  N  shows  a  concrete  bot- 
tom with  brick  sides,  having  the  pipe  supported  upon  cast- 
iron  standards.  The  latest  conduit  has  concrete  slabs  for 
bottom  and  sides  and  has  a  reinforced  concrete  slab  top. 
This  conies  as  near  being  permanent  as  any,  is  reasonable 
in  price,  and  when  the  interior  is  filled  with  good  non-con- 
ducting material,  or  when  the  pipe  is  covered  with  a  good 
sectional  covering,  it  gives  fairly  high  efficiency. 

All  conduits  should  be  run  as  nearly  level  as  possible 
to  avoid  the  formation  of  air  pockets  in  the  main.  Any  un- 
usual elevation  in  any  part  of  the  main  may  require  an  air 
vent  being  placed  at  the  uppermost  point  of  the  curve,  other- 
wise air  may  form  in  such  quantities  as  to  retard  circulation. 

136.  Layout  of  Street  Mains  and  Conduits: — No  definite 
information  can  be  given  concerning  the  layout  of  street 
mains,  because  the  requirements  of  each  district  would  call 
for  independent  consideration.  The  following  general  sug- 
gestions, however,  can  be  noted  as  applying  to  any  hot 
water  or  steam  system: 

Streets  to  be  used. — Avoid  the  principal  streets  in  the  city, 
especially  those  that  are  paved;  alleys  are  preferred  because 
of  the  minimum  cost  of  installation  and  repairs. 

Cutting  of  the  Mains. — Do  not  cut  the  main  trunk  line  for 
branches  more  often  than  is  necessary.  Provide  oc- 
casional by-pass  lines  between  the  main  branches  at  the  most 
important  points  in  the  system,  so  that,  if  repairs  are  being 


DISTRICT  HEATING 


189 


made  on  any  one  line,  the  circulation  beyond  that  point  may 
be  handled  through  the  by-pass.  Such  by-pass  lines  should 
be  valved  and  used  only  in  case  of  emergency. 

Offsets  and  Expansion  Joints. — Offsets  in  the  lines  hinder 
the  free  movement  of  the  water  and  add  friction  head  to  the 
pumps;  hence,  in  water  systems,  the  number  should  be  re- 
duced to  a  minimum.  Long  radius  bends  at  the  corners  re- 
duce this  friction.  Offsets  are  especially  valuable  to  take 
up  the  expansion  and  contraction  of  the  piping  without  the 
aid  of  expansion  joints.  This  is  illustrated  in  !E  ig.  89,  where 
anchors  are  placed  at  A,  and  the  gradual  bending  of  the 
pipes  at  each  corner  makes  the  necessary  allowance.  The 
expansion  in  wrought  iron  is  about  .00008  inch  per  foot  per 
degree  rise  in  temperature;  hence  in  a  hot  water  main  the 
linear  expansion  between  0°  and  212°  is  .017  inch  per  foot  of 
length  or  1.7  inches  for  each  100  feet  of  straight  pipe.  In 
hot  water  heating  systems,  however,  the  temperature  of  thid 
pipe  should  never  be  less  than,  say,  50°,  which  would  cause 
an  expansion  from  hot  to  cold  of  only  .013  inch  per  foot,  or 
1.3  inches  for  each  100  feet  of  straight  pipe.  In  a  steam  main 
the  temperature  may  vary  anywhere  from  50°  to  300°,  making 
a  lineal  expansion  of  .02  inch  per  foot  of  length  or  2  inches 
for  each  100  feet  of  straight  pipe.  As  here  shown  the 

movement  from  the  anchor 
at  A  toward  B  may  be  absorbed 
by  the  swinging  of  the  pipe 
about  O.  B.B.  should  therefore 
be  as  long  as  possible,  say  one 
full  block,  to  avoid  unduly 
straining  the  pipe  at  the 
joints.  Allowing  a  maximum 
movement  of  6  inches  for 


Fig.   89. 


each  expansion  joint,  the  anchors  would  be  spaced  500  and 
300  feet  center  to  center  respectively,  fcr  hot  water  and 
steam  mains.  These  figures  would  seldom  be  exceeded,  and 
in  some  cases  would  be  reduced,  the  spacing  depending 
upon  the  type  of  expansion  joint  used.  Ordinarily,  400  feet 
spacing  would  be  recommended  for  hot  water  and  300  feet 
for  steam.  If  the  city  layout  meets  this  value  fairly  well, 
then  the  expansion  joints  and  anchors  may  be  made  to 
alternate  with  each  other,  one  each  to  every  city  block. 


190  HEATING  AND  VENTILATION 


Fig.   90. 


DISTRICT  HEATING  191 

A  few  of  the  expansion  joints  in  common  use  are  shown 
In  Fig.  90.  A  is  the  old  slip  and  packed  joint.  This  joint 
causes  very  little  trouble  except  that  it  needs  repacking 
frequently.  It  is  very  effective  when  properly  cared  for. 
The  slip  joint  should  have  bronze  bearings  on  both  the 
outside  of  the  plug  and  the  lining  of  the  sleeve.  The  ends 
of  the  plug  and  sleeve  may  be  screwed  for  small  pipes, 
or  flanged  for  large  ones.  B  shows  an  improved  type  of 
slip  joint,  having  a  roller  bearing  upon  a  plate  in  the 
bottom  of  the  conduit,  and  plugs  bearing  against  metal 
plates  along  the  sides  of  the  conduit  to  keep  it  in  line.  G 
and  D  show  other  slip  joints  very  similar  to  A  and  B.  C 
has  one  ball  and  socket  end  to  adjust  the  joint  to  slight 
changes  in  the  run  of  the  pipe,  and  D  has  two  packings 
enclosing  the  plug  to  give  it  rigidity.  The  drainage  in 
each  case  is  taken  off  at  the  bottom  of  the  casting.  E 
has  two  large  flexible  disks  fastened  to  the  ends  of  the 
pipe  and  separated  from  each  other  by  an  annular  ring 
casting.  These  disks  are  frequently  corrugated,  are  usually 
of  copper  and  are  very  large  in  diameter  so  that  the  pipe 
has  considerable  movement  without  endangering  the  metal 
in  the  disks.  F  has  a  corrugated  copper  tube  fastened  at 
the  ends  to  the  pipe  flanges.  This  is  protected  from  ex- 
cessive internal  pressure  by  a  straight  tube  having  a  sli- 
ding fit  to  the  inside  of  the  flanges,  thus  allowing  for  end 
movement.  G  is  very  similar  to  E.  It  has,  however,  only 
one  copper  disk.  This  disk  is  enclosed  in  a  cast  iron  case- 
ment, one  side  of  which  is  open  to  the  atmosphere,  the 
other  side  having  the  same  pressure  as  within  the  pipe. 
H  is  very  similar  to  E,  having  two  copper  diaphragms  to 
take  up  the  movement.  These  diaphragms  flex  over  rings 
with  curved  edges  and  are  thus  protected  somewhat  against 
failure.  I  shows  a  copper  U  tube  which  is  sometimes  used. 
This  is  set  in  a  horizontal  position  and  the  expansion  and 
contraction  is  absorbed  by  bending  the  loop.  In  all  these 
joints  those  which  depend  upon  the  bending  of  the  metal 
require  little  attention  except  where  complete  rupture  oc- 
curs. In  old  plants,  however,  the  rupturing  of  these  dia- 
phragms is  of  frequent  occurrence.  The  packed  joint  re- 
quires attention  for  packing  several  times  in  the  year,  but 
very  seldom  causes  trouble  other  than  this. 


192 


HEATING  AND  VENTILATION 


Anchors. — In  any  long  run  of  pipe,  where  the  expansion 
and  contraction  of  the  pipe  causes  it  to  shift  its  position  very 
much,  it  is  necessary  to  anchor  the  pipe  at  intervals  so  as  to 
compel  the  movement  toward  certain  desired  points.  The 
anchor  is  sometimes  combined  with  the  expansion  joint,  in 
which  case  the  conduit  work  is  simplified.  See  Fig.  91. 

Service  pipes  to  residences  are  taken  off  at  or  near  the 
anchors.  All  condensation  drains  in  steam  mains  are  like- 
wise taken  off  at  such  points. 


Fig.    91. 


Valves. — All  valves  on  water  systems  should  be  straight- 
way gate  valves.  Valves  on  steam  systems  should  be  gate 
valves  on  lines  carrying  condensation,  and  renewable  seat 
globe  valves  on  the  steam  lines.  Valves  should  be  placed  on 
the  main  trunk  at  the  power  plant,  on  all  the  principal 
branch  mains  as  they  leave  the  main  trunk,  on  all  by-pass 
lines,  on  all  the  service  mains  to  the  houses,  and  at  such 
important  points  along  the  mains  as  will  enable  certain 
portions  of  the  heating  district  to  be  shut  off  for  repairs 
without  cutting  out  the  entire  district. 


DISTRICT  HEATING 


193 


Manholes. — Manholes  are  placed  at  important  points  along 
the  line  to  enclose  expansion  joints  and  valves.  These  man- 
holes are  built  of  brick  or  concrete  and  covered  with  iron 
plates,  flag  stones,  slate  or  reinforced  concrete  slabs.  Care 
must  be  exercised  to  drain  these  points  well  and  to  have  the 
covering  strong  enough  to  sustain  the  superimposed  loads. 

137.  Typieal  Design  for  Consideration: — In  discussing  dis- 
trict heating,  each  important  part  of  the  design  work  will 
be  made  as  general  as  possible  and  will  be  closed  by 
an  application  to  the  following  concrete  example  which  re- 
fers to  a  certain  portion  of  an  imaginary  city,  Fig.  92, 
as  available  territory.  A  city  water  supply  and  lighting 
plant  is  located  as  shown,  with  lighting  and  power  units  ag- 
gregating 475  K.  W.,  city  water  supply  pumps  aggregating 
3000000  gallons  maximum  capacity,  and  smaller  units  re- 
quiring approximately  15  per  cent,  of  the  amount  of 
steam  used  by  the  larger  lighting  units,  all  as  stated  in  gen- 
eral instructions.  Chapter  XVI.  It  is  desired  to  redesign 
this  plant  and  to  add  a  district  heating  system  to  it;  the  same 


Fig.    92. 


194 


HEATING  AND  VENTILATION 


to  have  all  the  latest  methods  of  operation  and  to  be  of  such  a 
size  as  to  be  economically  handled.  Fig.  99  shows  the  essen- 
tial details  of  the  finished  plant.  , 

138.  Electrical  Output  and  Exhaust  Steam  Available  for 
Heating  Purposes  Prom  the  Power  Units: — In  the  operation 
of  such  a  plant,  one  of  the  principal  assets  is  the  amount  of 
exhaust  steam  available  for  heating  purposes.  The  amount 
may  be  found  for  any  time  of  the  day  or  night  by  construct- 
ing a  power  chart  as  in  Pig.  93,  and  a  steam  consumption 
chart  as  in  Fig.  94.  Referring  to  Fig.  93,  the,  values  here 


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Fig.    93. 


given  are  assumed,  for  illustration,  to  be  those  recorded  at 
the  switch  board  of  the  typical  plant  on  a  day  when  heavy 
service  is  required.  The  curves  show  that  the  75  KW.  unit 
runs  from  12  P.  M.  to  7  A.  M.  and  from  6  P.  M.  to  12  P.  M. 
with  an  output  of  25  KW.  It  also  runs  from  7  A.  M.  to  10  A. 
M.  and  from  4  P.  M.  to  6  P.  M.  under  full  load.  The  150  KW. 
unit  runs  from  4  A.  M.  to  7  A.  M.  with  an  output  of  100  KW. 
and  then  increases  to  125  KW.  for  the  entire  time  until  6  P.  M. 
when  it  is  shut  down.  The  250  KW.  unit  is  started  up  at  7 
A.  M.  and  runs  until  6  P.  M.  under  full  load,  when  the  load 
drops  off  to  150  KW.  and  continues  until  10  P.  M.  when  the 
unit  is  shut  down,  leaving  only  the  75  KW.  unit  running.  The 
heavy  solid  line  shows  all  the  power  curves  superimposed 
one  upon  the  other.  Having  given  the  KW.  output,  the  gen- 


DISTRICT  HEATING 


195 


eral  formula  for  determining  the  horse  power  of  the  engines  is 

KW.  X  1000 


I.  H.  P.  = 


(69) 


746  X  E  X  E' 

where  E  and  E'  are  the  efficiencies  of  the  generator  and  en- 
gine respectively.  If  we  assume  the  efficiency  of  the  gener- 
ator to  be  90  per  cent.,  and  that  of  the  engine  to  be  92  per 
cent.,  then  formula  69  becomes, 

KW.  X  1000 

/.  H.  P.  = =  approx,  1.62  KW.       (70) 

746  X   .90  X   .92 

Assuming  that  the  250  KW.  unit  consumes  24  pounds,  the 
150  KW.  unit  32  pounds,  and  the  75  KW.  unit  32  pounds  of 
steam  per  /.  H.  P.  hour  respectively,  when  running  under 
normal  loads,  we  have  the  total  steam  consumed  in  the  three 
units  at  any  time  shown  by  the  lower  curve  in  Fig.  94. 


zzooo  - 

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1     ! 

•H 

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tut 

1  8000  ^ 

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IOOOOQ 

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8000  R- 

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4oco  - 

2000  ~ 

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rss; 

rn                             a.n                            n.                            f.n.                            p. 

HOURS. 

Fig.    94. 

The  upper  curve  shows  the  15  per  cent,  added  allowance  for 
the  smaller  units.  The  values  assumed  for  efficiencies  and 
the  values  for  steam  consumption  are  reasonable,  and  may  be 
used  if  a  more  exact  figure  is  not  to  be  had. 

It  will  be  seen  that  the  maximum  steam  consumption  in 
the  generating  units  in  the  power  plant  is  23100  pounds  per 
hour  and  the  minimum  is  1490  pounds  per  hour.  These  two 


196  HEATING  AND  VENTILATION 

amounts,  then,  together  with  the  exhaust  steam  from  the 
circulating  pumps  on  the  heating  system,  if  a  hot  water 
system  is  installed,  and  that  from  the  pumps  in  the  city 
water  supply,  will  determine  the  capacity  of  the  exhaust 
steam  heaters  on  the  hot  water  supply  and  the  capacity  of 
the  boilers  or  economizers  to  be  used  as  heaters  when  the 
exhaust  steam  is  deficient. 

139.  Amount  of  Heal  Available  for  Heating:  Purposes 
in  Exhaust  Steam,  Compared  with  That  in  Saturated  Steam 
at  the  Pressure  of  the  Exhaust: — To  study  the  effect  of  ex- 
haust steam  upon  heating  problems  and  to  determine,  if 
possible,  the  theoretical  amount  of  heat  given  off  with 
the  exhaust  steam  under  various  conditions  of  use,  let  us 
make  several  applications:  first,  to  a  simple  high  speed 
non  condensing  engine  using  saturated  steam;  second,  to 
a  compound  Corliss  non  condensing  engine  using  saturated 
steam;  third,  to  the  first  application  when  superheated 
steam  is  used  instead  of  saturated  steam;  and  fourth,  to  a 
horizontal  reciprocating  steam  pump.  Assume  the  follow- 
ing safe  conditions:  Case  one — boiler  pressure  100  pounds 
gage;  pressure  of  steam  entering  cylinder  97  pounds  gage; 
quality  of  steam  at  cylinder  98  per  cent.;  steam  consump- 
tion 34  pounds  per  indicated  horse  power  hour;  one  per 
cent,  loss  in  radiation  from  cylinder;  and  exhaust  pressure 
2  pounds  gage.  Case  2 — boiler  pressure  125  pounds  gage; 
pressure  at  high  pressure  cylinder  122  pounds  gage;  quality 
of  steam  entering  high  pressure  cylinder  98  per  cent.; 
steam  consumption  22  pounds  per  indicated  horse  power 
hour;  2  per  cent,  loss  in  radiation  from  cylinders  and  re- 
ceiver pipe,  and  exhaust  pressure  2  pounds  gage.  Case 
three — same  as  case  one  with  superheated  steam  at  150  de- 
grees of  superheat;  Case  four — as  stated  later. 

The  number  of  B.  t.  u.  exhausted  with  the  steam,  in 
any  case,  is  the  total  heat  in  the  steam  at  admission,  minus 
the  heat  radiated  from  the  cylinder,  minus  the  heat  ab- 
sorbed in  actual  work  in  the  cylinder. 

High  Speed  Engine.  Case  One.— Let  r  —  heat  of  vapor- 
ization per  pound  of  steam  at  the  stated  pressure, 'a?  =  qual- 
ity of  the  steam  at  cut  off,  q  —  heat  of  the  liquid  in  the 
steam  per  pound  of  steam,  and  W8  =  pounds  of  steam  per 


DISTRICT  HEATING  197 

indicated  horse  power  hour.  From  this  the  total  number 
of  B.  t.  u.  entering  the  cylinder  per  horse  power  hour  is 

Total  B.  t.  u.  —  Ws  (xr  +  q)  (71) 

From  Peabody's  Steam  tables  r  =  881,  x  =  .98  and  q  =  307; 
then  if  Wa  =  34,  Initial  B.  t.  u.  =  34  (.98  X  881  +  307)  = 
39792.92.  Deducting  the  heat  radiated  from  the  cylinder 
we  have  39792.92  X  .99  =  39395  B.  t.  u.  per  horse  power 
left  to  do  work.  The  B.  t.  u.  absorbed  in  mechanical  work 
(useful  work  +  friction)  in  the  cylinder  per  horse  power 
hour  is  (33000  X  60)  -H  778  =  2545  B.  <t.  u.  Subtracting 
this  work  loss  we  have  39395  —  2545  =  36850  B.  t.  u.  given 
up  to  the  exhaust  per  horse  power  hour.  Comparing  this 
value  with  the  total  heat  in  the  same  weight  of  saturated 
steam  at  2  pounds  gage,  we  have  100  X  36850  -i-  (34  X 
1152.8)  =  94  per  cent. 

Compound  Corliss  Engine.  Case  Two. — With  the  same  terms 
as  above  let  r  =  867.4,  x  =  .98,  q  =  324.4,  and  Ws  =  22, 
then  the  initial  B.  t.  u.  =  22(.98  X  867.4  -=-  324.4)  =  25837.9. 
Less  2  per  cent,  radiation  losses  =  25837.9  X  .98  =  25321.14 
B.  t.  u.  The  loss  absorbed  in  doing  mechanical  work  in  the 
cylinder  per  horse  power  is,  as  before,  2545  B.  t.  u.  Sub- 
tracting this  we  have  25321.14  —  2545  =  22776.14  B.  t.  u. 
given  up  to  the  exhaust  per  horse  power  hour.  Comparing 
as  before  with  saturated  steam  at  2  pounds  gage,  we  have 

100   X   22776.14  -f-   (22   X    1152.8)    =   90   per  cent. 

Case  three. — Now  suppose  superheated  steam  be  used  in 
the  first  application,  all  other  conditions  being  the  same, 
the  steam  having  150  degrees  of  superheat,  what  difference 
will  this  make  in  the  result?  The  total  heat  entering  the 
cylinder  now  is  the  total  heat  of  the  saturated  steam  at 
the  initial  pressure  plus  the  heat  given  to  it  in  the  super- 
heater. Let  Cp  =  specific  heat  of  superheated  steam  and 
td  —  the  degrees  of  superheat,  then  the  total  heat  of  the 
superheated  steam  is 

Total  B.  t.  u.  (sup.)  =  W8  (xr  +  q  +  Cpta)  (72) 

This  for  one  horse  power  of  steam  (34  pounds),  if  the 
specific  heat  of  superheated  steam  is  .54,  would  be  34  X  .99 
X  (1188  +  .54  X  150)  =  42714.5  B.  t.  u.  and  the  heat  turned 
into  the  exhaust  will  be  42714.5  —  2545  =  40169.5  B.  t.  u. 
Comparing  this  with  the  heat  in  saturated  steam  at  2 
pounds  gage,  we  have  100  X  40169.5  -r-  (34  X  1152.8)  =  102 
per  cent. 


198  HEATING  AND  VENTILATION 

Case  four. — Pump  exhausts  are  sometimes  led  into  the 
supply  and  used  for  heating-  purposes  along  with  the  engine 
exhausts.  If  such  conditions  he  found,  what  is  the  heating 
value  of  such  steam?  Assume  the  live  steam  to  enter  the 
steam  cylinder  of  the  pump  under  the  same  pressure  and 
quality  as  recorded  for  the  high  speed  engine.  The  steam 
is  cut  off  at  about  %  of  the  stroke  and  expands  to  the  end 
of  the  stroke.  With  this  small  expansion  the  absolute 
pressure  at  the  end  of  the  stroke  would  be  approximately 
%  X  112  =  98  pounds,  and,  if  enough  heat  is  absorbed  from 
the  cylinder  wall  to  bring  the  steam  up  to  saturation  at 
the  release  pressure,  we  will  have  a  total  heat  above  32 
degrees,  in  the  exhaust  steam  per  pound  of  steam  at  98 
pounds  absolute,  of  1185.6  B.  t.  u.  Comparing  this  with  a 
pound  of  saturated  steam  at  2  pounds  gage,  we  have 
100  X  1185.6  -=-  1152.8  =  103  per  cent.  Under  the  con- 
ditions such  as  here  stated  with  a  high  release  pressure, 
a  small  expansion  of  steam  in  the  cylinder  and  dry  steam 
at  the  end  of  the  stroke,  it  is  possible  to  suddenly  drop  the 
pressure  from  pump  release  to  a  low  pressure,  say  2  pounds 
gage,  and  have  all  the  steam  brought  to  a  state  approach- 
ing superheat.  It  is  not  likely,  however,  that  the  steam 
is  dry  at  the  end  of  the  stroke  in  any  pump  exhaust,  be- 
cause the  heat  lost  in  radiation  and  in  doing  work  in  the 
slow  moving  pump  would  be  such  as  to  have  a  considerable 
amount  of  entrained  water  with  the  steam,  thus  lowering 
the  quality  of  the  steam.  These  above  conditions  are  ex- 
treme and  are  not  obtained  in  practice. 

From  cases  one  and  two  it  would  appear  that  the 
greatest  amount  of  heat  that  can  be  expected  from  engine 
exhausts,  for  use  in  heating  systems  at  or  near  the  pres- 
sure of  the  atmosphere,  is  90  to  94  per  cent,  of  that  of 
saturated  steam  at  the  same  pressure.  The  percentage 
will,  in  most  cases,  drop  much  below  this  value.  All 
things  considered,  exhaust  steam  having  80  to  85  per  oent.  of  the 
value  of  saturated  steam  at  the  same  pressure  is  probably  the  safest 
rating  when  calculating  the  amount  of  radiation  which  can  be  sup- 
plied by  the  engines.  In  many  cases  no  doubt  this  could  be 
exceeded,  but  it  is  always  best  to  take  a  safe  value.  On 
the  other  hand,  when  figuring  the  amount  of  condenser  tube  sur- 
face or  reheater  tube  surface  to  condense  the  steam,  it  would 
be  best  to  take  exhaust  steam  at  100  per  cent,  quality,  since  this 
would  be  working  toward  the  side  of  safety. 


DISTRICT  HEATING  199 

In  plants  where  the  exhaust  steam  is  used  for  heating 
purposes  and  where  the  amount  supplied  by  direct  acting 
steam  pumps  is  large  compared  with  that  supplied  by  the 
power  units,  it  is  possible  to  have  the  quality  of  the  ex- 
hausts anywhere  between  800  and  1000  B.  t.  u.  per  pound 
of  exhaust.  It  should  be  understood  that  saturated  steam 
at  any  stated  pressure  always  has  the  same  number  of 
B.  t.  u.  in  it,  no  matter  whether  it  is  taken  directly  from 
the  boiler,  or  from  the  engine  exhaust.  A  pound  of  the 
mixture  of  steam  and  entrained  water,  taken  from  engine 
exhausts,  should  not  be  considered  as  a  pound  of  steam. 
If  we  are  speaking  of  a  pound  of  exhaust  steam  without 
the  entrained  water  as  compared  with  a  pound  of  saturated 
steam  at  the  same  pressure,  they  are  the  same,  but  a  pound 
of  engine  exhaust  or  mixture  is  a  different  thing. 


200 


HEATING  AND  VENTILATION 


HOT    WATER    SYSTEMS. 

140.  Two  General  Classifications  of  hot  water  heating, 
and  a  number  of  modifications  of  these,  may  be  found  in 
current  work.  The  power  plant  apparatus  for  each  of 
these  systems  is  all  very  much  the  same,  but  the  outside 
work  in  the  two  general  systems  is  entirely  different.  The 
first,  known  as  the  one-pipe  complete  circuit  system,  is  shown 


POWER  HOUSE. 


Fig.    95. 


in  Fig.  95.  It  will  be  noticed  that  the  water  leaves  the 
power  plant  and  makes  a  complc-ta  circuit  of  the  district, 
as  A,  B,  C,  D,  E,  F,  O,  through  a  single  pipe  of  uniform 
diameter.  From  this  main  is  taken  branch  mains  and 
leads  to  the  various  houses,  as  a,  6,  c  and  d,  e,  each  one  re- 
turning to  the  principal  main  after  having  made  its  own 
minor  circuit.  The  other  is  known  as  the  two-pipe  high 
pressure  system,  in  which  two  main  pipes  of  like  diameter 
laid  side  by  side  in  the  same  conduit,  radiate  from  the 
power  plant  to  the  farthest  point  on  the  line  reducing 
in  size  at  certain  points  to  suit  the  capacity  of  that  part 
of  the  district  served.  This  system  is  represented  by  Fig. 
96.  In  the  one-pipe  system  the  circulation  in  the  various 


DISTRICT  HEATING 


201 


residences  is  maintained,  in  part,  by  what  is  known  as  the 
shunt  system,  and  in  part,  by  the  natural  gravity  cir- 
culation. The  circulation  in  the  two-pipe  system  is  main- 
tained by  a  high  differential  pressure  between  the  main 
and  the  return  at  the  same  point  of  the  conduit.  The  force 
producing  movement  of  the  water  in  the  shunt  system  is, 
therefore,  very  much  less  than  in  the  two-pipe  system.  As  a 
consequence,  the  one-pipe  system  has  a  lower  velocity  of  the 
water  in  the  houses  and  larger  service  pipes  than  the  two- 
pipe  system. 


~r=\ 


POWER  Hou&t 


Fig.    96. 


In  many  cases  it  is  desired  to  connect  central  heating 
mains  to  the  low  pressure  hot  water  systems  in  private 
plants.  Such  connections  may  easily  be  made  with  either 
one  of  the  two  systems  by  installing  some  minor  pieces 
of  apparatus  for  controlling  the  supply. 

141.  Amount  of  Water  Needed  Per  Hour  as  a  Heating 
Medium: — All  calculations  must  necessarily  begin  with  the 
heat  lost  at  the  residence.  Referring  to  the  Standard  room 
mentioned  in  Art.  78,  we  find  the  heat  loss  to  be  14000  B.  t.  u. 
per  hour,  requiring  84  square  feet  of  hot  water  heating  sur- 
face to  heat  the  room.  Let  the  circulating  water  have  the 
following  temperatures:  leaving  the  power  plant  180*,  enter- 
ing the  radiator  177°,  leaving  the  radiator  157°,  and  entering 


202  HEATING  AND  VENTILATION 

the  power  plant  155°.  According  to  these  figures,  which  may 
be  considered  fair  average  values,  the  water  gives  off  to  the 
radiator  20  B.  t.  u.  per  pound  or  166.6  B.  t.  u.  per  gallon,  thus 
requiring  14000  -r-  166.6  —  84  gallons  of  water  per  hour  to 
maintain  the  room  at  a  temperature  of  70°.  From  this  a 
fairly  safe  estimate  may  be  given,  i.  e.,  each  square  foot  of  hot 
water  radiation  in  the  city  will  require  approximately  one  gallon  of 
water  per  hour.  It  is  very  certain  that  some  plants  are  de- 
signed to  supply  less  than  this  amount,  but  in  such  cases  it 
requires  a  higher  temperature  of  the  circulating  water  and 
allows  little  chance  for  future  expansion  of  the  plant.  A 
drop  of  20  degrees,  i.  e.,  20  B.  t.  u.  heat  loss  per  pound  of  water 
passing  through  the  radiator,  is  probably  a  maximum  and  in- 
dicates the  minimum  amount  of  water  that  should  be  circu- 
lated. In  practice,  this  heat  loss  would  probably  be  nearer 
15  B.  t.  u.  per  pound,  and  consequently  would  necessitate  the 
use  of  somewhat  more  than  one  gallon  of  water  per  square 
foot  of  heating  surface  per  hour.  All  things  considered,  the 
above  italicised  statement  will  satisfy  every  condition.  Hav- 
ing the  total  number  of  square  feet  of  radiation  in  the  dis- 
trict, the  total  amount  of  water  circulated  through  the  mains 
per  hour  can  be  obtained,  after  which  the  size  of  the  pumps 
in  the  power  plant  may  be  estimated. 

142.  Radiation  in  the   District: — The   amount   of   radia- 
tion that  may  be  installed  in  the  district  is  problematical.     In 
an  average  residence  or  business  district  the  following  fig- 
ures  may   easily   be   realized:    business   square,   9000  square  feet; 
residence  square,  4500  square  feet.     In  certain  locations  these  fig- 
ures may  be   exceeded  and  in   others   they  may   be   reduced. 
Where  the  needs  of  the  district  are  thoroughly  understood  a 
miore  careful  estimate  can  easily  be  made.     It  is  always  well 
to  make  the  first  estimate  a  safe  one  and  any  possible   in- 
crease above  this  figure   could  be  taken  care  of  as   in  Art. 
141.      Referring    to   Fig.    92,    an    estimate    of    the    amount    of 
radiation   that  may  be   expected   in  this  typical   case,   if  we 
assume    ten    business    squares    and    twenty-one     residence 
squares,  is  184500  square  feet.     This  will  call  for  the  circu- 
lation of  184500  gallons  of  water  per  hour. 

143.  Future  Increase  in  Radiation: — From  the  tempera- 
tures given  in  Art.  141,  it  will  be  seen  that  each  pound  of 
water  takes  on  25  B.  t.  u.  at  the  power  plant  and  that  there 


DISTRICT  HEATING  203 

is  a  possible  increase  of  212  —  180  =  32  B.  t.  u.  per  pound  that 
may  be  given  to  it,  thus  increasing  the  capacity  of  the  system 
approximately  125  per  cent.  It  would  not  be  safe  to  count 
on  such  an  increase  in  the  average  plant  because  of  a  defec- 
tive layout  in  the  piping  system  or  because  of  a  low  ef- 
ficiency in  some  of  the  pumps  or  other  apparatus  in  the 
plant.  If,  however,  a  plant  is  installed  according  to  the  above 
figures,  the  capacity  may  be  quite  materially  increased  by 
increasing  the  temperature  of  the  outgoing  water  at  the 
plant  to  212°. 

144.  The  Pressure  of  the  Water  In  the  Mains: — The  ele- 
vation above  the  plant  at  which  a  central  station  can  supply 
radiation  is  limited.  Water  at  180°  will  weigh  60.55  pounds 
per  cubic  foot,  and  the  pressure  caused  by  an  elevation  of  1 
foot  is  .42  pound  per  square  inch.  From  this  the  static  pres- 
sure at  the  power  plant,  due  to  a  hydraulic  head  of  100  feet, 
is  42  pounds  per  square  inch.  This  value  should  not  be  ex- 
ceeded, and  generally,  because  of  the  influence  it  has  on  the 
machines  and  pipes  toward  producing  leaks  or  complete 
ruptures,  a  less  head  than  this  is  desirable.  A  static  pres- 
sure of  42  pounds  may  be  expected  to  produce,  in  a  well  de- 
signed plant,  an  outflow  pressure  of  65  to  75  pounds  per 
square  inch  and  a  return  pressure  of  15  to  20  pounds  per 
square  inch,  when  working  under  fairly  heavy  service.  In 
any  case  where  the  mains  are  too  small  to  supply  the  radia- 
tion in  the  system  properly,  we  may  expect  the  value  given 
for  the  outflow  to  increase  and  that  for  the  return  to  de- 
crease. A  safe  set  of  conditions  to  follow  is:  head,  in  feet, 
60;  static  pressure,  in  pounds  per  square  inch,  25;  outgoing 
pressure  at  the  pumps,  in  pounds  per  square  inch,  60;  return 
pressure  at  the  pumps,  in  pounds  per  square  inch,  15. 
This  differential  pressure  of  45  pounds  is  caused  by  the 
friction  losses  in  the  piping  system,  pumps  and  heaters. 
Long  pipe  systems,  as  these  are  called,  have  much  greater 
friction  losses  in  the  long  runs  of  piping  than  in  the  ells, 
tees,  valves,  etc.,  hence,  the  friction  head  of  the  pipes  is  all 
that  is  usually  considered.  Where  the  minor  losses  are 
thought  to  be  large,  they  may  be  accounted  for  by  adding 
to  the  pipe  loss  a  certain  percentage  of  itself. 


204  HEATING  AND  VENTILATION 

The  maximum  pressure  in  the  system  is  due  to  two 
causes;  first,  the  static  head,  and  second,  the  frictional  re- 
sistances. The  first  is  easily  estimated  when  the  static 
head  is  known.  To  obtain  the  second,  formula  73  is  rec- 
ommended. See  Merriman's  "A  Treatise  on  Hydraulics," 
Arts.  86  and  100,  and  Church's  "Mechanics  of  Engineering", 
Art.  519. 

(frl  Vs 

nf  =  —x-  (73) 

d         2g 

where  lif  =  feet  of  head  lost  in  friction,  $  =  friction  factor 
(synonomous  with  coefficient  of  friction.  For  clean  cast 
iron  pipes  with  a  velocity  of  5  to  6  feet  per  second  this 
has  been  found  to  vary  from  .024  to  .019,  for  diameters 
between  3  and  15  inches  respectively.  .02  is  suggested  as 
a  safe  average  value  to  use),  I  =  length  of  pipe  in  feet, 
v  =  velocity  of  the  water  in  feet  per  second,  d  =  diameter 
of  pipe  in  feet  and  2g  =  64.4. 

APPLICATION.— In  Fig.  96,  let  it  be  desired  to  find  the 
differential  pressure  at  the  pumps  due  to  the  friction  losses 
in  the  line  A,  B,  C,  D,  E.  The  lengths  of  the  various  parts 
are:  power  plant  to  A,  200  feet;  A  to  B,  500  feet;  B  to  C, 
1500  feet;  C  to  D,  1500  feet,  and  D  to  E,  500  feet. 
Assume,  for  illustration,  that  the  total  radiation  in  square 
feet  beyond  each  of  these  points  is,  power  plant,  125000: 
A,  85000;  B,  50000;  C,  28000  and  D,  12000.  This  requires 
125000,  85000,  50000,  28000  and  12000  gallons  of  water  per 
hour,  or  4.74,  3.27,  1.75,  1  and  .44  cubic  feet  of  water  per 
second,  respectively,  passing  these  points.  Now,  if  the 
velocities  be  roughly  taken  at  6  and  5  feet  per  second, 
(pipes  near  the  power  plant  may  be  g-iven  somewhat  higher 
velocities),  the  pipes  will  be  12,  10,  8,  6  and  4  inches  diam- 
eter. In  applying  the  formula  to  one  part  of  the  line  we 
show  the  method  employed  for  each.  Take  that  part  from 
the  power  plant  to  A.  With  v  =  6 

.02  X  200  X  36 

Jif  = =2.2  feet 

64.4   X   1 

It  should  be  noted  here  that  formula  73  refers  to  pipes 
where  all  the  water  that  enters  at  one  end  passes  out  the  other. 
This  is  not  true  in  heating  mains  where  a  part  of  the 


DISTRICT  HEATING 


205 


water  is  drawn  off  at  intermediate  points.  On  the  other 
hand,  Merriman,  Art  99,  explains  that  a  water  service  main, 
where  the  water  is  all  taken  off  from  intermediate  tappings  and 
where  tne  velocity  at  the  far  end  is  zero,  causes  only  one-third 
of  the  friction  given  by  the  above  formula.  The  case  under 
consideration  falls  somewhere  between  these  two  extremes, 
the  part  next  the  power  plant  approaching  the  former  and 
the  last  part  of  the  line  exactly  meeting  the  conditions  of 
the  latter.  Assuming  the  mean  of  these  two  conditions, 
which  is  probably  very  close  to  the  actual,  gives  two-thirds 
of  that  found  by  the  formula.  Now  since  this  is  a  double 
main  system,  i.  e.,  main  and  return  of  the  same  size,  the 
friction  head  for  the  two  lines  becomes  2.94  feet,  from 
the  power  plant  to  A.  In  a  similar  way  the  other  parts 
may  be  tried  and  the  results  from  the  entire  line  assembled 
in  convenient  form  as  in  Table  XXVII. 


TABLE  XXVII. 


P.  P. 
to  A. 

A  toB 

B  to  C 

C  to  D 

Dto  E 

.Distance  between  points  
Radiation  supplied  

200 
125000 

500 
85000 

1500 
50000 

1500 
28000 

500 
12000 

Volume  of  water  passing  point 
in  cu.  ft.  per  sec. 

4-74 

8  27 

1-75 

1. 

•  44 

Velocity  f.  p,  s. 

6 

Q 

5 

5 

5 

Area  of  pipe  sq.  ft. 

.79 

545 

.85 

.20 

.087 

Diam.  of  pipe  in  ft. 

1 

.83 

.66 

•  5 

.38 

hf  by  (78)  for  flow  main..  . 

2.2 

6.7 

17.4 

23  8 

11.7 

7.V  (taking  §  value) 

1.47 

4.47 

11.6 

15.5 

7.8 

hf  (§  val.  flow  and  return)  

2.94 

8-94 

28-2 

81.0 

15.6 

From  the  last  line  of  the  table  we  obtain  the  total 
friction  head  for  both  mains,  not  including  ells,  tees,  valves, 
etc.,  to  be  81.6  feet.  This  is  equivalent  to  34.3  pounds  per 
square  inch.  Now  if  we  allow  about  20  per  cent,  of  all  the 
line  losses  to  cover  the  minor  losses  we  have  approximately 
40  pounds  differential  pressure,  which  is  a  reasonable 
value. 

145.  Velocity  of  the  Water  in  the  Mains  and  the  Di- 
ameter of  the  Mains: — The  district  is  first  chosen  and  the 
layout  of  the  conduit  system  is  made.  This  is  done  inde- 
pendently of  the  sizes  of  the  pipes.  When  this  layout  Is 
finally  completed,  the  pipe  sizes  are  roughly  calculated  for 


206  •       HEATING  AND  VENTILATION 

all  the  important  points  in  the  system  a.nd  are  tabulated 
in  connection  with  the  friction  losses  for  these  parts,  as 
in  Art.  144.  When  this  is  d/>ne,  formula  74,  which  is  rec- 
ommended to  be  used  in  connection  with  (73),  may  be 
applied  and  the  theoretical  diameters  found.  (The  approx- 
imate diameters  and  the  friction  heads  need  not  be  calcu- 
lated in  (73)  for  use  in  (74)  providing  some  estimate  may 
be  made  for  the  value  hf,  for  the  various  lengths  of  pipe. 
If  desired,  hf  may  be  assumed  without  any  reference  to  the 
diameter,  but  this  is  a  rather  tedious  process.  For  good 
discussion  of  this  point  see  Church's  Hydraulic  Motors, 
Art.  121.) 

$IQ 
d  =    .479/%   X   -  (74) 


where  d,  hf,  0  and  I  are  the  .same  as  in  (73),  and  Q  =  cubic 
feet  of  water  passing  through  the  pipe  per  second.  This 
formula  differs  from  those  given  in  the  references  stated, 
in  that  the  term  %  is  inserted  as  a  mean  value  between 
the  two  extreme  conditions,  as  stated  in  Art.  144. 

APPLICATION.  —  Let  it  be  desired  to  find  the  diameter  for 
the  single  main  between  the  power  plant  and  A,  Art.  144, 
with  hf  =  1.47 

2  X  .02  X  200  X  (4.74)2       V5 

d  —    .479    (  -  :  ----  \      =   1    ft.  =  12   in. 
^  3   X   1.47  ' 


Applying  to  the  entire  line  with  hf  as  given  in  next  to  last 
line  of  Table  XXVII,  gives  power  plant  to  A,  d  =  12  inches; 
A  to  B,  d  =  10  inches;  B  to  C,  d  =  8  inches;  C  to  D,  d  =  6 
inches;  and  D  to  E,  d  =  4  inches. 

In  some  cases,  when  close  estimating  is  not  required, 
it  is  satisfactory  to  assume  a  velocity  of  the  water  and  find 
the  diameter  without  considering  the  friction  loss.  In 
many  cases,  however,  this  would  soon  prove  a  positive  loss 
to  the  Company.  With  a  .low  velocity,  the  pipe  would  be 
large,  the  first  cost  would  be  large  and  the  operating  cost 
would  be  low.  On  the  other  hand,  if  the  velocity  were 
high,  the  pipe  would  be  small,  the  first  cost  would  be 
small  and  the  operating  cost  and  depreciation  would  be 
large.  As  an  illustration  of  how  the  friction  head  in- 
creases in  a  pipe  of  this  kind  with  increased  velocity, 


DISTRICT  HEATING         .  207 

refer  to  the  run  of  mains  between  B  and  C.  Assuming  a 
velocity  of  10  feet  per* second,  which  in  this  case  would  be 
very  high,  the  friction  head,  hf,  for  the  single  main,  be- 
comes 62  and  the  theoretical  diameter  is  5.5,  say  6  inches. 
The  friction  head,  as  will  be  seen,  is  5.4  times  the  cor- 
responding value  when  the  velocity  was  5  feet  per  second. 
Since  the  pump  must  work  continually  against  this  head, 
it  would  incur  a  financial  loss  that  would  soon  exceed  the 
extra  cost  of  installing  larger  pipes.  It  is  found  in  plants 
that  are  in  first  class  operation  that  the  velocities  range 
from  5  to  7  feet  per  second. 

The  calculations  in  Arts.  144  and  145  are  very  much 
simplified  by  the  use  of  the  chart  shown  in  the  Appendix. 
In  planning  a  system  of  this  kind,  find  the  friction  head 
on  the  pumps  and  the  diameters  of  the  pipes  for  various 
velocities,  say  4,  6,  8  and  10  feet  per  second.  Estimate  the 
probable  first  cost  and  the  depreciation  of  the  conduit 
system  for  each  velocity,  and  balance  these  figures  with 
the  operating  cost  for  a  period  of,  say  five  years,  to  see 
which  is  the  most  economical  velocity  to  use  in  figuring 
the  system. 

146.  Service  Connections  are  usually  installed  from   30 
to  36   inches  below  the  surface  of  the  ground,  and  are   in- 
sulated in  some  form  of  box  conduit  which  compares  favor- 
ably with  that  of  the  main  conduit.     Service  branches  are 
li/4,    IVa    and   2   inch   wrought   iron   pipe.      These   are   usually 
carried    to    the    building    from    the    conduit    at    the    expense 
of    the    customer.      Such    branch    conduits    are    not    drained 
by   tile   drains. 

147.  Total    Steam  Available   and  B.  t.  u.   Liberated   per 
Hour   for   Heating   the    Circulating   Water: — The    amount    of 
steam   available   for   heating   the   circulating   water    is   that 
given   off   by  the   generating   units,   plus   that   from   the   cir- 
culating pumps,  plus  that  from  the  city  water  supply  pumps 
if  there  be  any,  plus  that  from  the  auxiliary  steaming  units 
in  the  plant,  i.  e.,  small  pumps,  engines,  etc.     In  the  typical 
application   this   amounts   to   23100   +   12720   +   8680   =   44500 
pounds  per  hour. 

This  steam,  of  course,  is  not  equal  to  good  dry  steam  in 
heating  value  because  of  the  work  it  has  done  in  the  engine 


208  HEATING  AND  VENTILATION 

and  pump  cylinders,  but  a  good  estimate  of  its  value  may 
be  approximated.  In  addition  to  the  terms  used  in  for- 
mula 71,  let  q'  —  heat  in  the  returning  condensation  per 
pound;  then  the  heat  available  for  heating-  purposes  per 
pound  of  exhaust  steam  is 

B.  t.  u.  =  xr  +  q  —  q'  (75) 

It  is  probably  safe  to  consider  the  quality  of  the  steam  as 
85  per  cent,  of  that  of  good  dry  steam  at  the  same  pressure. 
Since  the  pressure  of  the  exhaust  from  a  non  condensing 
engine,  as  it  enters  the  heater,  is  near  that  of  the  atmosphere, 
and  since  the  returning  condensation  is  at  a  temperature  of 
about  180°,  the  total  amount  of  heat  given  off  from  a  pound 
of  exhaust  steam  to  the  circulating  water  is 

B.  t.  u.  =  .85  X  969.7  +  180.3  —  (180.54  —  32)  =  856,  say  850. 

If  Wt  be  the  pounds  of  exhaust  steam  available,  the  total 
number  of  B.  t.  u.  given  off  from  the  exhaust  steam  per  hour  is 

Total   B.   t.   u.  =   850  Wa  (76) 

Applying  this  to  the  typical  power  plant  gives  850  X 
44500  —  37825000  B.  t.  u.  per  hour.  This  amount  is  probably 
a  maximum  under  the  conditions  of  lighting  units  as  stated, 
and  would  be  true  for  only  5  hours  out  of  24.  At  other  times 
the  exhaust  steam  drops  off  from  the  lighting  units  and  this 
deficiency  must  be  made  good  by  heating  the  circulating 
water  directly  from  the  coal,  by  passing  the  water  through 
heating  boilers  or  by  passing  it  through  economizers  where 
it  is  heated  by  the  waste  heat  from  the  stack  gases. 

148.  Amount  of  Hot  Water  Radiation  in  the  District 
that  can  be  Supplied  by  One  Pound  of  Exhaust  Steam  on  a 
Zero  Day: — In  Art.  141,  each  pound  of  water  takes  on  25 
B.  t.  u.  in  passing  through  the  reheaters  at  the  power  plant, 
and  gives  off  at  least  20  B.  t.  u.  in  passing  through  the 
radiator.  The  number  of  pounds  of  water  heated  per  pound 
of  steam  per  hour  is,  Wv  =  (Total  B.  t.  u.  available  per 
pound  of  exhaust  steam  per  hour)  -~  25,  and  the  total  radi- 
ation that  can  be  supplied  is 

Total  B.t.u.  available  per  Ib.  of  exhaust  steam  per  hr. 

RW  — (77) 

8.33   X   25 


DISTRICT  HEATING  209 


which  for  average  practice  reduces  to 

850 

Rw  = =:  4  square  feet  approx.  (78) 

208 

Applying-  formula  77  for  the  five  hour  period  when  the 
exhaust  steam  is  maximum  gives  Rw  —  37825000  -^  208  = 
181851  square  feet.  It  is  not  safe  to  figure  on  the  peak  load 
conditions.  It  is  better  to  assume  that  for  half  the  time, 
35000  pounds  of  steam  are  available  and  will  heat  35000 
X  4  =  140000  square  feet  of  radiation. 

149.  The  Amount  of  Circulating;  Water  Passe*!  through 
the    Heater   Necessary   to    Condense    One    Pound   of   Exhaust 
Steam  is 

Total  B.t.u.  available  per  Ib.  of  exhaust  steam  per  hr. 

Wv, (79) 

25 

With    the    value    given    above    for   the    exhaust    steam    this 
becomes,    for    100    and    85    per    cent,    respectively, 

1000 

Ww  =  =   40   pounds  (80) 

25 

850 

Ww  —  —  34  pounds  (81) 

25 

150.  Amount    of    Hot    Water    Radiation    in    the    District 
tlisit  can  be  Heated  by  One  Horse   Power  of  Exhaust   Steara 
from   a   Non   Condensing   Engine   on   a   Zero   Day: — 

Rw  =  4  X  (pounds  of  steam  per  H.  P.  hour)  (82) 

This  reduces  for  the  various  types  of  engines,  as  follows: 

Simple    high    speed  4   X   34   =  136  square  feet. 

"        medium  "  4   X   30  =  120          "  " 

Corliss  4  X   26   =  104 

Compound  high  "  4X26  =  104 

"    medium    "  4   X   25   =  100 

"    Corliss  4   X   22  =     88 

151.  Amount  of  Radiation  that  can  be  Supplied  by  Ex- 
haust  Steam   in  Formulas  77   and  78   at   any  other  Temper- 
ature   of   the    "Water,    fw,    than    that    stated,    with    the    Room 


210 


HEATING  AND  VENTILATION 


Temperature,  t',  remaining  the  same: — The  amount  of  heat 
passing  through  one  square  foot  of  the  radiator  to  the  room 
is  in  proportion  to  tw  —  t'.  In  formulas  77  and  78,  tw  —  V  — 
100.  Now  if  tw  be  increased  x  degrees,  so  that  tw  —  tf  = 
(100  +  x),  then  each  square  foot  of  radiation  in  the  building 

100  +  x 
will    give    off 


times    more    heat    than    before    and 


100 


each  pound  of  exhaust   steam  will  supply  only 

4    X    100 

square  feet 


(83) 


100   +  x 

This  for  an  increase  of  30  degrees,  which  is  probably  a  max- 
imum, is 

4 

Rw  = =  3  square  feet  (84) 

1.3 

Compared  with  (78),  formula  83  shows,  with  a  high  tem- 
perature of  the  water  entering  the  radiator,  that  less  radi- 
ation is  necessary  to  heat  any  one  room  and  that  each 
square  foot  of  surface  becomes  more  nearly  the  value  of  an 
equal  amount  of  steam  heating  surface.  Calculations  for 
radiation,  however,  are  seldom  made  from  high  temper- 
atures of  the  water,' and  this  article  should  be  considered 
an  exceptional  case. 

152.  Exhaust  Steam  Condenser  (Reheater),  for  Reheat- 
ing the  Circulating  Water: — In  the  layout  of  any  plant 
the  reheaters  should  be  located  close  to  the  circulating 
pumps  and  on  the  high  pressure  side.  They  are  usually  of 
the  surface  condenser  type,  Fig.  97,  and  may  or  may  not  be 
installed  in  duplicate.  Of  the  two  types  shown  in  the  fig- 
ure, the  water  tube  type  is  probably  the  more  common.  The 
same  principles  hold  for  each  in  design.  In  ordinary  heaters 
for  feed  water  service,  wrought  iron  tubes  of  iy2  to  2  inches 


WATET?  TUBE  TVPt 


WATEP 

STEAM  TUBLTVPE 


Fig.    97. 


DISTRICT  HEATING  211 

diameter  are  generally  used,  but  for  condenser  work  and 
where  a  rapid  heat  transmission  is  desired,  brass  or  copper 
tubes  are  used,  having  diameters  of  %  to  1  inch.  In  heating 
the  circulating  water  for  district  service,  the  reheater  is 
doing  very  much  the  same  work  as  if  used  on  the  condens- 
ing system  for  engines  or  turbines.  The  chief  difference  is  in 
the  pressures  carried  on  the  steam  side,  the  reheater  con- 
densing the  steam  near  atmospheric  pressure  and  the  con- 
denser carrying  about  .9  of  a  perfect  vacuum.  In  either  case 
it  should  be  piped  on  the  water  side  for  water  inlet  and  out- 
let, while  the  steam  side  should  be  connected  to  the  exhaust 
line  from  the  engines  and  pumps,  and  should  have  proper 
drip  connections  to  draw  the  water  of  condensation  off  to  a 
condenser  pump.  This  condenser  pump  usually  delivers  the 
water  of  condensation  to  a  storage  tank  for  use  as  boiler 
feed,  or  for  use  in  making  up  the  supply  in  the  heating  sys- 
tem. 

In  determining  the  details  of  the  condenser  the  following 
important  points  should  be  investigated:  the  amount  of 
heating  surface  in  the  tubes,  the  size  of  the  water  inlet  and 
outlet,  the  size  of  the  pipe  for  the  steam  connection,  the  size 
of  the  pipe  for  the  water  of  condensation  and  the  length 
and  cross  section  of  the  heater. 

153.     Amount  of  Heating  Surface  in  the  Reheater  Tubes: 

— The  general  formula  for  calculating  the  heating  surface  in 
the  tubes  of  a  reheater  (assuming  all  heating  surface  on 
tubes  only),  is 

Total  B.  t.  u.  given  up  by  the  exhaust  steam  per  hr 

Rt   =  (85) 

K  (Temp.  diff.  between  inside  and  outside  of  tubes) 

The  maximum  heat  given  off  from  one  pound  of  exhaust 
steam  in  condensing  at  atmospheric  pressure  is  1000  B.  t.  u., 
the  average  temperature  difference  is  approximately  47 
degrees,  and  K  may  be  taken  427  B.  t.  u.  per  degree  dif- 
ference per  hour.  In  determining  K,  it  is  not  an  easy  mat- 
ter to  obtain  a  value  that  will  be  true  for  average  practice. 
Carpenter's  H.  &  V.  B.  Art.  47  quotes  the  above  figure  for 
tests  upon  clean  tubes,  and  volumes  of  water  less  than 
1000  pounds  per  square  foot  of  heating  surface  per  hour. 
It  is  found,  however,  that  the  average  heater  or  condenser 


212  HEATING  AND  VENTILATION 

tube  with  its  lime  and  mud  deposit  will  reduce  the  efficiency 
as  low  as  40  to  50  per  cent,  of  the  maximum  transmission. 
Assume  this  value  to  be  45  per  cent.;  then  if  Wa  is  the 
number  of  pounds  of  available  exhaust  steam,  formula  85 
becomes 

1000  TF,                   1000  W,                 1000  W,             W, 
Rt  — = — _ (86) 

K(t,— tw)        427  X   .45  X  47  9031  9.1 

In  "Steam  Engine  Design,"  by  Whitham,  page  283,  the 
following  formula  is  given  for  surface  condensers  used  on 
shipboard: 

W  L 


S  = 


CK  (!»,.  — 


where  £  =  tube  surface,  W  =  total  pounds  of  exhaust  steam 
to  be  condensed  per  hour,  L  =  latent  heat  of  saturated  steam 
at  a  temperature  Tit  K  —  theoretical  transmission  of  B.  t.  u. 
per  hour  through  one  square  foot  of  surface  per  degree  dif- 
ference of  temperature  =  556.8  for  brass,  c  =  efficiency  of 
the  condensing  surface  =  .323  (quoted  from  Isherwood),  TI  = 
temperature  of  saturated  steam  in  the  condensers,  and  *  — 
average  temperature  of  the  circulating  water. 
"With  L  =  969.7,  c  =  .323,  K  =  556.8  and  TI  —  t  —  47,  we 
may  state  the  formula  in  terms  of  our  text  as 


969.7  W*  W* 

Rt  = = = (87) 

.323  X  556.8  X  47  8446  8.7 

In  Sutcliffe  "Steam  Power  and  Mill  Work,"  page  512,  the 
author  states  that  condenser  tubes  in  good  condition  and  set 
in  the  ordinary  way  have  a  condensing  power  equivalent  to 
13000  B.  t.  u.  per  square  foot  per  hour,  when  the  condensing 
water  is  supplied  at  60  degrees  and  rises  to  95  degrees  at  dis- 
charge, although  the  author  gives  his  opinion  that  a  trans- 
mission of  10000  B.  t.  u.  per  square  foot  per  hour  is  all  that 
should  be  expected.  This  checks  closely  with  formula  86, 
which  gives  the  rate  of  transmission  9031  B.  t.  u.  per  square 
foot  per  hour. 

The  following  empirical  formula  for  the  amount  of  heat- 
ing surface  in  a  heater  is  sometimes  used: 

Rt    =    .0944    Ws  (88) 

Where  the  terms  are  the  same  as  before. 


DISTRICT  HEATING  213 

APPLICATION.  —  Let  the  total  amount  of  exhaust  steam  avail- 
able for  heating  the  circulating-  water  be  35000  pounds  per 
hour,  the  pressure  of  the  steam  in  the  condenser  be  atmos- 
pheric and  the  water  of  condensation  be  returned  at  180°; 
also,  let  the  circulating  water  enter  at  155°  and  be  heated  to 
180°.  These  values  are  good  average  conditions.  The  assump- 
tion that  the  pressure  within  the  condenser  is  atmospheric 
might  not  be  fulfilled  in  every  case,  but  can  be  approached 
very  closely.  From  these  assumptions  find  the  square  feet 
of  surface  in  the  tubes. 

35000 
Formula  86,  Rt  =  -  =  3846  sq.  ft. 

9.1 

35000 
Formula  87,  Rt  =  -  =  4023  sq.  ft. 

8.7 
Formula  88,  Rt  =  35000   X    .0944  =  3304  sq  ft. 

1000  X   35000 

•Satellite         Rt   =  --  =   3500    sq.    ft. 
10000 

If   3846   square   feet   be   the   accepted   value   it   will   call   for 
three  heaters  having  1282  square  feet  of  tube  surface  each. 

154.  Amount  of  Reheater  Tube  Surface  per  Engine  Horse 
Power:  —  Let  tcs  be  the  pounds  of  steam  used  per  I.  H.  P.  of 
the  engine;  then  from  formula  86 


Rt  (per  /.  H.  P.)  =  -  (89) 

9.1 

This  reduces  for  the  various  types  of  engines  as  follows: 

Simple  high  speed  34  -=-  9.1  =  3.74  square  feet 

"     medium       "  30  -J-  9.1  =  3.30 

"     Corliss  26  -T-  9.1  =  2.86 

Compound  high  "  26  ^  9.1  =  2.86 

"     medium  "  25  -j-  9.1  =  2.75 

"     Corliss  22  -H  9.  1=2.  42 

155.  Amount  of  Hot  Water  Radiation  in  the  District 
that  can  he  Supplied  by  One  Square  Foot  of  Reheater  Tube 
Surface:  —  If  the  transmission  through  one  square  foot  of 


214  HEATING  AND  VENTILATION 

tube   surface   be  K    (ts  —  £w)   =  9031   B.   t.    u.    per  hour  and 
the  amount  of  heat  needed  per  square  foot  of  radiation  per 

hour  =  8.33  X  25  =  208,  as  given  in  formula  77,  then 

9031 
Rw  (per  sq.  ft.  of  tube  surface)  = =  43 . 4  sq.  ft.       (90) 

208 

156.  Some  Important  Reheater  Details: — Inlet  and  Outlet 
Pipes: — Having  three  heaters  in  the  plant,  it  seems  rea- 
sonable that  each  heater  should  be  prepared  for  at  least  one- 
third  of  the  water  credited  to  the  exhaust  steam.  From 
Art.  148  this  is  140000  -f-  3  =  46667  gallons  =  10800000  cubic 
inches  per  hour.  The  velocity  of  the  water  entering  and 
leaving  the  heater  may  vary  a  great  deal,  but  good  values 
for  calculations  may  be  taken  between  5  and  7  feet  per 
second.  Assuming  the  first  value  given,  we  have  the  area 
of  the  pipe  =  10800000  -f-  (5  X  12  X  3600)  =  50  square  inches, 
and  the  diameter  8  inches. 

The  Size  of  the  Reheater  Shell. — Concerning  the  velocity 
of  the  water  in  the  reheater  itself,  there  may  be  dif- 
ferences of  opinion;  100  feet  per  minute  will  be  a  good  value 
to  use  unless  this  value  makes  the  length  of  the  tube  too 
great  for  its  diameter.  If  this  is  the  case  the  tube  will  bend 
from  expansion  and  from  its  own  weight.  At  this  velocity 
the  free  cross  sectional  area  of  the  tubes,  assuming  the  water 
to  pass  through  the  tubes  as  in  Fig.  97,  would  be  150 
square  inches.  If  the  tubes  be  taken  %  inch  outside  diam- 
eter, with  a  thickness  of  17  B.  W.  G.,  and  arranged  as  usual 
in  such  work,  it  will  require  about  475  tubes  and  a  shell 
diameter  of  approximately  30  inches.  If  the  inner  surface  of 
the  tube  be  taken  as  a  measurement  of  the  heating  surface 
and  the  total  surface  be  1282  square  feet,  the  length  of  the 
reheater  tubes  would  be  approximately  16  feet. 

The  ratio  of  the  length  of  the  tube  to  the  diameter  is, 
in  this  case,  256,  about  twice  as  much  as  the  maximum  ratio 
used  by  some  manufacturers.  It  would  be  better  therefore 
to  increase  the  number  rf  tubes  and  decrease  the  length. 
With  a  velocity  of  the  water  at  50  feet  per  minute,  the 
values  will  be  approximately  as  follows;  free  cross  sec- 
tional area  of  the  tubes,  300  square  inches;  number  of  tubes, 
950;  diameter  of  shell,  40  inches;  length  of  tubes,  8  feet. 
These  values  check  fairly  well  and  could  be  used. 


DISTRICT  HEATING  215 

The  Size  of  the  Exhaust  Steam  Connection. — To  calculate  this, 
use  the  formula 

144  g, 
-—  (91) 

where  <?.»  =  volume  of  steam  in  cubic  feet  per  minute,  V  — 
velocity  in  feet  per  minute,  and  A  —  area  of  pipe  in  square 
inches.  When  applied  to  the  reheater  using  35000  pounds 
of  steam  per  hour,  at  26  cubic  feet  per  pound  and  at  a  veloc- 
ity through  the  exhaust  pipe  of  6000  feet  per  minute,  it  gives 
144  X  35000  X  26 

A  = =  360sq.  in.  =  22   in.  dia. 

60  X  6000 
Try  also,  from  Carpenter's  H.  &  V.  B.,  page  284. 


.23  (92) 

Allowing  30  pounds  of  steam  per  H.  P.  hour  for  non  condens- 
ing engines  we  have  35000  -r-  30  =  1166  horse  power;  then 
applying  the  above  we  obtain  d  =  16  inches.  Comparing 
the  two  formulas,  91  and  92,  the  first  will  probably  admit  of  a 
more  general  application.  The  velocity  6000  for  exhaust  steam 
may  be  increased  to  8000  for  very  large  pipes  and  should  be 
reduced  to  4000  for  small  pipes.  In  the  above  applications 
a  20-inch  pipe  will  suffice. 

The  Return  Pipe  for  Condensation. — The  diameter  of  the 
pipe  leading  to  the  condenser  pump  will  naturally  be 
taken  from  the  catalog  size  of  the  pump  installed.  This 
pump  would  be  selected  from  capacities  as  guaranteed  by 
the  respective  manufacturers  and  should  easily  be  capable  of 
handling  the  amount  of  water  that  is  condensed  per  hour. 

The  Value  of  a  High  Pressure  Steam  Connection. — If  desired, 
the  reheater  may  also  be  provided  with  a  high  pres- 
sure steam  connection,  to  be  used  when  the  exhaust  steam 
is  not  sufficient.  This  steam  is  then  used  through  a  pres- 
sure-reducing valve  which  admits  the  steam  at  pressures 
varying  from  atmospheric  to  5  pounds  gage.  There  is  some 
question  concerning  the  advisability  of  doing  this.  Some 
prefer  to  install  a  high  pressure  steam  heater,  as  in  Art.  157, 
to  be  used  independently  of  the  exhaust  steam  heaters.  This 
removes  all  possibility  of  having  excessive  back  pressure 
on  the  engine  piston,  as  is  sometimes  the  case  where  high 
pressure  steam  is  admitted  with  the  exhaust  steam. 


216 


HEATING  AND  VENTILATION 


It  has  been  the  experience  of  some  who  have  operated 
such  plants  that  where  more  heat  is  needed  than  can  be 
supplied  by  the  exhaust  steam,  it  is  better  to  resort  to  heat- 
ing boilers  and  economizers,  than  to  use  high  pressure  steam 
for  heating. 

157.  High  Pressure  Steam  Heater: — When  this  heater  is 
used  it  is  located  above  the  boiler  so  that  all  the  condensa- 
tion freely  drains  back  to  the  boilers  by  gravity  as  in  Fig. 
98.  In  calculating  the  tube  surface,  use  formula  85  with 
the  full  value  of  the  steam  and  the  steam  temperatures 
changed  to  suit  the  increased  pressure.  Such  a  heater  as 
this  gives  good  results. 


Fig.    98. 


158.  Circulating  Pumps: — Two  types  of  pumps  are  in 
general  use:  centrifugal  and  reciprocating.  Each  type  is 
somewhat  limited  in  its  operation.  The  centrifugal  pump 
has  difficulty  in  operating  against  high  heads  and  the  recip- 


DISTRICT  HEATING  217 

rocating  pump  is  very  noisy  when  running  at  a  high  piston 
speed.  Since  each  type  is  in  successful  operation  in  many 
plants,  no  comparisons  will  be  made  between  them  further 
than  to  say  that  the  former,  being  operated  by  a  steam  en- 
gine, may  be  run  more  economically  than  the  latter  because 
of  the  possibilities  of  using  the  steam  expansively.  It  will 
be  noted,  however,  that  this  same  steam  is  to  be  used  in  the 
exhaust  steam  heaters  for  warming  the  circulating  water 
and  hence  there  would  be  little,  if  any,  direct  loss  from  this 
source  in  the  use  of  the  reciprocating  pump. 

Having  given  the  maximum  amount  of  water  to  be 
circulated  per  hour,  consult  trade  catalogs  and  select  the 
number  of  pumps  and  the  size  of  each  pump  to  be  installed. 
The  sizes  of  the  pumps  can  easily  be  determined  when  the 
number  of  them  has  been  decided  upon.  This  latter  point 
is  one  upon  which  a  difference  of  opinion  will  probably  be 
found.  No  exact  rule  can  be  applied.  In  a  plant  of,  say 
not  more  than  150000  square  feet  of  radiation  (150000  gal- 
lons of  water  per  hour,  or  3  million  gallons  for  twenty-four 
hours),  some  designers  would  put  in  three  pumps,  each 
having  1.5  million  gallons  capacity;  in  which  case  one 
pump  could  be  cut  out  for  repairs  and  the  other  two  would 
be  able  to  care  for  the  service  temporarily.  Other  designers 
would  use  four  pumps  at  about  one  million  gallons  each. 
The  fewer  the  pumps  installed,  in  any  case,  the  greater 
should  be  the  capacity  of  each.  The  following  values  will 
be  found  fairly  satisfactory: 

1  Pump.  Cap.  =  (1  to  1.25)   times  max.  requirem't  of  system 

2  Pumps.  "  (each)  =  .75    "  "       "  "   " 

3  Pumps.  "   "     =  .5     "  "       "  "   " 

4  Pumps.  "    "     =  .3     "  "       "  "   " 

Having  given  the  capacity  of  each  pump  in  gallons  of 
water  per  minute,  the  size,  the  horse  power  and  the  steam 
consumption  of  each  pump  can  be  calculated.  In  obtaining 
the  size  of  the  pump  it  will  be  necessary  to  know  the  speed, 
V,  of  the  piston  in  feet  per  minute,  the  strokes,  N,  per  minute 
and  the  per  cent,  of  slip,  s  (100  per  cent.  — 8,  where  S  =  hy- 
draulic efficiency).  The  speed  varies  between  100,  for  small 
pumps,  and  75,  for  large  pumps.  The  strokes  vary  between 
200,  for  small  pumps,  and  40,  for  large  pumps,  and  the  slip 
varies  between  5  and  40  per  cent.,  depending  upon  the  fit  of 


218  HEATING  AND  VENTILATION 

the  piston  and  the  valves.     In  pumps  that  have  been  in  serv- 
ice for  some  time  the  slip  will  probably  average  20  per  cent. 
The  cross  sectional  area  of  the  water  cylinder  in  square 
inches   is 

cubic  inches  pumped  per  minute 

W.  C.  A.  = (93) 

8  X  V  X  12 

from  which  we  may  obtain  the  diameter  of  the  water  cylinder. 
The  steam  cylinder  area  is  usually  figured  as  a  certain 
ratio  to  that  of  the  water  cylinder  area;  as, 

8.  C.  A.  =  (1.5  to  2.5)    X  W.  C.  A.  (94) 

from  which  we  may  obtain  the  diameter  of  the  steam  cylin- 
der. 

The  length  of  the  stroke,  L,  in  incnes,  will  be  obtained 
from  the  speed  and  the  number  of  strokes  such  that, 

12  V 
*  =  _  (.6) 

All  direct  acting  steam  pumps  are  designated  by  diam- 
eter of  steam  cylinder  X  diameter  of  water  cylinder  X  length 
of  stroke;  as, 

14"   X    12"   X    18" 

Duplex  pumps  have  twice  the  capacity  of  single  pumps 
having  the  same  sized  cylinders. 

To  find  the  indicated  horse  power,  /.  H.  P.,  of  the  pumps, 
reduce  the  pressure  head,  p,  in  pounds  per  square  inch,  to 
pressure  head  in  feet,  h;  multiply  this  by  the  pounds  of 
water,  W,  pumped  per  minute  and  divide  the  product  by  33000 
times  the  mechanical  efficiency,  E. 

W  Ji 

I.  H.  P.  =  (96) 

33000  E 

To  reduce  from  pressure  head  in  pounds  to  pressure 
head  in  feet,  divide  the  pressure  head  in  pounds  by  weight 
of  a  column  of  water  one  square  inch  in  area  and  one  foot 
high.  The  general  equation  for  this  is 

144  p 
h  = 


w 

where  w  =  the  weight  of  a  cubic  foot  of  water  at  the  given 
temperature  and  p  —  differential  pressure  in  pounds  per 
square  inch. 


DISTRICT  HEATING  219 

In  pump  service  of  this  kind  the  pressure  head,  p,  against 
which  the  pump  is  acting,  is  not  the  result  of  the  static 
head  of  water  in  the  system  but  is  due  to  the  inertia  of  the 
water  and  to  the  resistance  to  the  flow  of  water  through 
the  piping  system  and  the  heaters.  This  frictional  resist- 
ance may  be  calculated  as  shown  in  Art.  144.  Read  this 
part  of  the  work  over  carefully. 

For  an  illustration  of  combined  pressure  head,  p,  and 
friction  head,  Jif,  see  Art.  161  on  boiler  feed  pumps.  Having 
found  the  7.  77.  P.  of  any  pump,  multiply  it  by  the  steam  con- 
sumption per  /.  H.  P.  hour  and  the  result  will  be  the  steam 
consumption  of  the  pump.  This  exhaust  steam  will  be  con- 
sidered a  part  of  the  general  supply  when  figuring  the  size 
of  the  exhaust  steam  heaters  in  the  system. 

The  mechanical  efficiency,  E,  of  piston  pumps  depends 
upon  the  condition  of  the  valves  and  upon  the  speed,  and 
varies  from  90  per  cent.,  in  new  pumps,  to  50  per  cent.,  in 
pumps  that  are  badly  worn.  A  fair  average  would  be  70 
per  cent. 

The  steam  consumption  for  reciprocating,  simple  and 
duplex  non  condensing  pumps  would  approximate  100  to 
200  pounds  of  steam  per  7.  77.  P.  hour — the  greater  values  re- 
ferring to  the  slower  speeds. 

159.  Centrifugal  Pumps: — Centrifugal  pumps  are  of 
two  classifications,  the  Volute  and  the  Turbine.  The  prin- 
ciples upon  which  each  operate  are  very  similar.  The  ro- 
tating impeller,  or  rotor,  with  curved  blades  draws  the 
water  in  at  the  center  of  the  pump  and  delivers  it  from  the 
circumference.  The  rotor  is  enclosed  by  a  cast  iron  case- 
ment which  is  shaped  more  or  less  to  fit  the  curvature  of 
the  edges  of  the  blades  on  the  rotor.  Centrifugal  pumps 
are  used  where  large  volumes  of  water  are  required  at  low 
heads.  They  are  used  in  city  water  supply  systems,  in  cen- 
tral station  heating  systems,  in  condenser  service,  in  irri- 
gation work  and  in  many  other  places  where  the  pressure 
head  operated  against  is  not  excessive.  The  efficiency  of 
the  average  centrifugal  pump  is  from  65  to  80  per  cent., 
75  per  cent,  being  nothing  uncommon.  In  places  where  such 
pumps  are  used  the  head  is  usually  below  75  feet,  although 
some  types,  when  direct  connected  to  high  speed  motors, 
are  capable  of  operating  against  heads  of  several  hundred 
feet. 


220  HEATING  AND  VENTILATION 

Some  of  the  advantages  of  centrifugal  pumps  over  hor- 
izontal reciprocating  pumps  are:  low  first  cost,  simplicity, 
few  moving  parts,  compactness,  uniform  flow  and  pressure 
of  water,  freedom  from  shock,  possibilities  of  having  them 
direct  connected  to  high  speed  motors  and  the  ability  to 
handle  dirty  water  without  injuring  the  pump. 

One  of  the  advantages  of  piston  pumps  over  centrifugal 
pumps  is  the  fact  that  they  are  more  positive  in  their  op- 
eration and  work  against  higher  heads. 

Centrifugal  pumps,  when  connected  to  engine  and  tur- 
bine drives,  benefit  by  the  expansion  of  the  steam  and  are 
much  more  economical  than  the  direct  acting  piston  pump, 
which  takes  steam  at  full  pressure  for  nearly  the  'entire 
stroke.  The  amount  of  steam  used  in  the  pumps  in  central 
station  work,  however,  is  not  a  serious  factor,  since  all  of 
the  heat  in  the  steam  that  is  not  used  in  propelling  the 
water  through  the  mains  is  used  in  the  heaters  to  increase 
the  temperature  of  the  water. 

The  sphere  of  usefulness  of  the  centrifugal  pump  in 
central  station  heating  is  increasing.  The  direct  acting 
piston  pump,  when  operating  at  fairly  high  speeds,  causes 
hammering  and  pounding  in  the  transmission  lines,  and 
these  noises  are  sometimes  conveyed  to  the  residences  and 
become  annoying  to  the  occupants.  This  feature  is  not  so 
noticeable  in  the  operation  of  the  centrifugal  pump. 

APPLICATION. — In  Art.  142  assume  the  capacity  of  the  plant, 
10  business  squares  and  21  residence  squares,  to  require 
184500  gallons  of  water  per  hour;  the  same  to  be  pumped 
against  a  pressure  head,  Art.  144,  of  60 — 15  pounds,  by 
horizontal,  direct  acting  piston  pumps.  Assume,  also  the 
steam  consumption  of  the  pumps  to  be  100  pounds  per  I.  H.  P. 
hour,  and  the  average  temperature  of  the  water  at  the 
pumps  to  be  (180  +  155)  -r-  2  =  167.5  degrees.  Apply  for- 
mula 96,  where  h  =  calculated  total  friction  head  for  the 
longest  line  in  the  system  (this  is  designated  by  lit  in  Art. 
144),  or  where  p  =•  total  difference  between  the  incoming 
and  the  outgoing  pressures.  With  the  weight  of  a  cubic 
foot  of  water  at  167.5  degrees  =  60.87  pounds  and  with 
p  =  45,  we  have  h  =  106.5  feet,  and  the  indicated  horse  power 
of  the  pumps,  assuming  65  per  cent,  mechanical  efficiency, 
is 

184500  X  8.33  X  106.5 

I.  H.  P.  — =127.2 

33000  X   .65  X  60 


DISTRICT  HEATING  221 


Prom  this  the  steam  consumption  will  probably  be  12720 
pounds  per  hour. 

If  centrifugal  pumps  were  selected,  the  horse  power 
would  be  calculated  from  the  same  formula,  but  the  steam 
consumption  would  probably  be  30  to  40  pounds  of  steam 
per  horse  power  hour  because  of  the  expansive  working  of 
the  steam. 

160.  City  Water  Supply  Pumps: — Horizontal,  direct  act- 
ing duplex  pumps  for  use  on  city  water  supply  service  are 
the   same   as   those   used  to   circulate   the   water   in   heating 
systems;  hence,  the  foregoing  descriptions  apply  here.     The 
/.  H.  P.  of  the  city  water  supply  pumps  would  be  calculated 
by  use  of  formula   96.     If  the  pumps  lifted  the  water  from 
the  wells,  as  would  probably  be  the  case,  the  suction  pres- 
sure  would   be    negative   and   would   be   added   to   the   force 
pressure. 

APPLICATION. — In  Art.  186  the  pressure  in  the  fresh  water 
mains  is  60  pounds  and  the  suction  pressure  is  10  pounds; 
therefore,  p  =  60  —  ( — 10)  —  70  pounds,  and,  with  the  water 
at  65  degrees,  h  =  144  X  70  4-  62.5  =  161  feet.  These  pumps 
are  each  rated  at  1.5  million  gallons  in  24  hours,  and  deliver 
62500  X  8.33  =  520833  pounds  of  water  per  hour,  when  run- 
ning at  full  capacity.  Assuming  each  pump  to  deliver  75  per 
cent,  of  the  full  requirement  of  the  system,  the  total  amount 
of  water  pumped  per  hour  for  the  city  water  supply  would 
approximate  520833  -f-  .75  =  694444  pounds,  and  the  total 
average  horse  power  used  in  pumping  the  water  would  be 

694444  X  161 

I.  H,  P  = =86.8 

60  X  33000  X  .65 

With  100  pounds  of  steam  per  horse  power  hour,  this  will 
amount  to  8680  pounds  of  steam  available  per  hour  for  use  in 
heating  the  circulating  water. 

161.  Boiler   Feed   Pumps: — Horizontal    pumps    for   high 
pressure  boiler  feeding  are  selected  in  a  similar  way  to  the 
circulating    pumps    for   the    city   water    supply.      Such    units 
are  called  auxiliary  steam  units  and,  because  the  steam  re- 
quired is  small,   they  are  sometimes   piped  to  a  feed  water 
heater  for  heating  the  boiler  feed.     The  velocity  of  the  water 
through  the   suction  pipe   is  about   200  feet  per  minute  and 


222  HEATING  AND  VENTILATION 

in  the  delivery  pipe  about  300  feet  per  minute.  The  piston 
speed,  the  strokes  per  minute  and  the  slip  would  be  very  much 
the  same  as  stated  under  circulating1  pumps.  Such  pumps 
should  have  a  pumping-  capacity  about  twice  as  great  as  the 
actual  boiler  requirements  and,  in  small  plants  where  only 
one  pump  is  needed,  the  installation  should  be  in  duplicate. 
The  sizes  of  the  cylinders  and  the  efficiencies  are  about  as 
stated  for  the  larger  circulating-  pumps. 

In  determining  the  horse  power  of  a  boiler  feed  pump, 
four  resistances  must  be  overcome;  i.  e.,  pressure  head,  p, 
or  boiler  pressure;  suction  head,  7ts;  delivery  head,  ha',  and 
the  friction  head,  hf.  The  first  three  values  are  usually  given. 
The  friction  head  includes  the  resistances  in  all  piping, 
ells  and  valves  from  the  supply  to  the  boiler.  The  friction 
in  the  piping-  may  be  taken  from  Table  32  or  it  may  be 
worked  out  by  formula  73.  The  friction  in  the  ells  and 
valves  is  more  difficult  to  determine  and  is  usually  stated 
in  equivalent  length  of  straight  pipe  of  the  same  diameter. 
A  rough  rule  used  by  some  in  such  cases  is  as  follows: 
"to  the  length  of  the  given  pipe,  add  60  times  the  nominal 
diameter  of  the  pipe  for  each  ell,  and  90  times  the  diameter 
for  each  globe  valve,"  then  find  the  friction  head  as  stated 
above.  A  straight  flow  gate  or  water  valve  could  safely  be 
taken  as  an  ell.  P  or  simplicity  of  calculation,  all  of  the 
above  resistances  may  be  reduced  to  an  equivalent  head, 
such  that 

144  p 


+  ha  +  h.  +  ht  (97) 


where  w  =  weight  of  one  cubic  foot  of  water  at  the  suc- 
tion temperature,  w  may  be  obtained  from  Table  6 
and  hf  may  be  taken  from  Table  32.  The  horse  power  by 
formula  96  then  becomes,  if  W  =  pounds  of  water  pumped 
per  minute, 

W  X  he 

I.  H.  P.  = (98) 

33000  E 

APPLICATION. — Let  p  =  125  pounds  gage,  to  =  62.5,  /Jd  =  8 
feet,  hs  =  20  feet,  horizontal  run  of  pipe  from  supply  to 
pump  =  20  feet,  horizontal  run  of  pipe  from  pump  to  boiler 
=  30  feet;  also,  let  the  pump  supply  89000  pounds  of  water 
per  hour  to  the  boiler.  This  is  twice  the  capacity  of  the 
boiler  plant.  With  this  amount  of  water  at  the  usual  veloc- 


DISTRICT  HEATING  223- 

ity  it  will  give  a  suction  pipe  of  4.5  inches  diameter,  and  a 
flow  pipe  of  4  inches  diameter.  Let  there  be  two  ells  and 
one  gate  valve  on  the  suction  pipe,  and  three  ells,  one  globe 
valve  and  one  check  valve  on  the  delivery  pipe.  We  then 
have  an  equivalent  of  107  feet  of  suction  pipe,  and  158  feet 
of  delivery  pipe.  Referring  to  Table  32,  hf  is  approxi- 
mately 7  feet,  and  the  total  head  is 

144  X  125 

he  = \-  8  +  20  +  7  =  323  feet. 

62.5 
In  most  boiler  feed  pumps  it  is  considered  unnecessary 

to  determine  lit  so  carefully.  A  very  satisfactory  way  is  to 
obtain  the  total  head  pumped  against,  exclusive  of  the 
friction  head,  and  add  to  it  5  to  15  per  cent.,  depending 
upon  the  complications  in  the  circuit.  Substituting  the 
above  in  formula  98,  we  obtain 

89000  X  323 

/.  H.  P.  = =  22.3 

60  X  33000  X   .65 

Work  out  the  value  hf  by  (73)  and  see  how  nearly  it 
checks  with  the  above. 

162.  Boilers: — A  number  of  boilers  will  necessarily  be 
installed  in  a  plant  of  this  kind,  and  a  good  arrangement  is  to 
have  them  so  piped  with  water  and  steam  headers  that  any 
number  of  the  boilers  may  be  used  for  steaming  purposes 
and  the  rest  as  water  heaters.  They  should  also  be  so  ar- 
ranged that  any  of  the  boilers  may  be  thrown  out  of  service 
for  cleaning  or  repairs  and  still  carry  on  the  work  of  the 
plant.  By  doing  this  the  boiler  plant  becomes  very  flexible 
and  each  boiler  is  an  independent  unit.  Any  good  water  tube 
boiler  would  serve  the  purpose,  both  as  a  steaming  and  as  a 
heating  boiler.  Where  the  boilers  are  used  as  heaters,  the 
water  should  enter  at  the  bottom  and  come  out  at  the  top. 
Where  the  water  enters  at  the  top  and  comes  out  at  the  bot- 
tom, the  excessive  heating  of  the  front  row  of  tubes  retards 
the  circulation  of  the  water  by  this  heat,  and  produces  a  rapid 
circulation  through  the  rear  tubes  where  the  heat  is  the 
least.  This  rapid  circulation  in  the  rear  tubes  is  not  a  detri- 
ment, but  it  is  less  needed  there  than  in  the  front  ones.  It 
would  be  decidedly  better  if  the  rapid  circulation  were  in  the 
front  row,  causing  the  heat  from  the  fire  to  be  carried  off 
more  readily,  and  by  this  means  giving  less  danger  of  burn- 
ing the  tubes.  In  the  latter  case  the  forced  circulation  from 
the  pumps  will  be  aided  by  the  natural  circulation  from  the 


224  HEATING  AND  \ENTILATION 

heat  of  the  fire,  and  the  life  of  all  the  tubes  then  becomes 
more  uniform.  Fig.  99  shows  a  typical  header  arrangement. 
Boilers  are  usually  classified  as  fire  tube  and  water  tube. 
Fire  tube  boilers  are  usually  of  the  multitubular  type,  having 
the  flue  gases  passing  through  the  tubes  and  water  sur- 
rounding them.  Water  tube  boilers  have  the  water  passing 
through  the  tubes  and  the  flue  gases  surrounding  them, 
The  heating  surface  of  a  boiler  is  composed  of  those  boiler 
plates  having  the  heated  flue  gases  on  one  side  and  the  water 
on  the  other.  A  toiler  horse  power  may  be  taken, as  follows: 

Centennial  Rating. 

One  B.  H.  P.  =  30  pounds  of  water  evaporated  from  feed 
water  at  100°  F.  to  steam  at  70  pounds  gage  pressure. 

A.    S.   M.    E.    Rating. 

One  B.  H.  P.  —  34.5  pounds  of  water  evaporated  from 
and  at  212°  F. 

In  laying  out  a  boiler  plant  some  good  approximations 
for  the  essential  details  are: 

One  B.  H.  P.  =  11.5  square  feet  of  heating  surface 

(multitubular  type). 
One  B.  H.  P.  =  10  square  feet  of  heating  surface 

(water   tube   type). 
One  B.  H.  P.  =  .33  square  feet  of  grate  surface 

(small   plant,   say   one   boiler). 
One    B.    H.    P.    —    .25    square    feet    of    grate    surface 

(medium  sized  plant,  say  500  H.  P.). 
One  B.  H.  P.  —  .20  square  feet  of  grate  surface 

(large    plants). 

Pounds  of  water  evaporated  per  square  foot  of  heating 
surface  per  hour  =  3  (approx.  value). 

163.  Square  feet  of  Hot  \Vater  Radiation  that  can  be 
Supplied  on  a  Zero  Day  by  One  Boiler  Horse  Power  when  the 
Boiler  is  Used  as  a  Heater: — Assuming  that  the  coal  used  in 
the  plant  has  a  heating  value  of  13000  B.  t.  u.  per  pound, 
and  that  the  efficiency  of  the  boiler  is  60  per  cent.,  each 
pound  of  coal  will  transmit  to  the  water  7800  B.  t.  u.  Since 
each  pound  of  water  takes  up  25  B.  t.  u.  on  its  passage 
through  the  heating  boiler,  one  pound  of  coal  will  heat  312 
pounds,  or  37.5  gallons  of  water.  This  is  equivalent  to 
supplying  heat,  under  extreme  conditions  of  heat  loss,  to 


DISTRICT  HEATING  225 

37.5  square  feet  of  radiation  for  one  hour.  One  boiler  horse 
power,  according  to  Art.  162,  is  equivalent  to  the  expendi- 
ture of  969.7  X  34.5  =  33455  B.  t.  u.  Now  since  each  pound 
of  coal  transfers  to  the  water  7800  B.  t.  u.,  one  boiler  horse 
power  will  require  33455  -^  7800  =  4.28  pounds  of  coal.  If, 
then,  the  burning  of  one  pound  of  coal  will  supply  37.5  square 
feet  of  hot  water  radiation  for  one  hour,  one  boiler  horse 
power  will  supply  4.28  X  37.5  =  160  square  feet  for  one 
hour,  and  a  100  H.  P.  boiler  will  supply  16000  square  feet 
of  water  radiation  in  the  district  for  the  same  time.  These 
figures  have  reference  to  boilers  under  good  working  con- 
ditions and  probably  give  average  results. 

164.  Square  Feet  of  Hot  Water  Radiation  in  the  District 
that  can  be  Supplied  on  a  Zero  Day  by  an  Economizer  Lo- 
cated in  the  Stack  Gases  between  the  Boilers  and  the  Chim- 
ney:— (In  order  to  make  this  estimate  it  is  necessary  first  to 
know  the  horse  power  of  the  boilers,  the  amount  of  coal 
burned  per  hour,  the  pounds  of  gases  passing  through  the 
furnace  per  hour  and  the  heat  given  off  from  these  gases 
to  the  circulating  water  through  the  tubes. 

APPLICATION.— Let  C  —  pounds  of  coal  burned  per  hour  =  boiler 
.horse  power  X  pounds  of  coal  per  boiler  horse  power  hour,  Wa 
=  pounds  of  air  passed  through  the  furnace  per  pound  of  fuel 
burned,  s  =  specific  heat  of  the  gases,  U  =  temperature  of 
gases  leaving  boiler,  ts  =  temperature  of  gases  leaving  econ- 
omizer, tw  =.  temperature  of  water  entering  economizer 
and  tf  =  temperature  of  water  leaving  the  economizer 
Then,  if  8.33  pounds  of  water  will  supply  one  square  foot 
of  radiation  for  one  hour  we  have, 

8  X   (C  X  Wa  +  O)   X   Us  —  U) 

Rw  =  (99) 

8.33   X    (tt  —  tw) 

Prom  a  previous  statement,  44500  pounds  of  steam 
per  hour  is  generated  in  the  steam  boiler  plant  at  a 
pressure  of  125  pounds  gage.  To  find  the  boiler  horse 
power,  let  the  total  heat  of  the  steam,  above  32°  at  125 
pounds  gage,  be  1191.8  B.  t.  u.,  and  let  the  temperature 
of  the  incoming  feed  water  to  the  boilers  be  60  degrees. 
(In  most  cases  the  feed  water  will  be  at  a  higher  tempera- 
ture, but  since  it  will  occasionally  be  as  low  as  60  degrees, 
this  value  will  be  a  fair  one.)  The  heat  put  into  a  pound 
of  steam  under  these  conditions  is  1191.8  —  (60 — 32)  =  1163.8 
B.  t.  u.,  and  in  44500  pounds  it  will  be  51789100  B.  t.  u. 


226  HEATING  AND  VENTILATION 

Since  one  horse  power  of  boiler  service  is  equivalent  to  33455 
B.  t.  u.,  we  will  need  51789100  -4-  33455  =  1548  boiler  horse 
power.  This  horse  power  will  take  care  of  all  the  engines 
and  pumps  in  the  plant.  If  the  coal  used  contains  13000 
B.  t.  u.  per  pound  and  the  boilers  have  60  per  cent,  effi- 
ciency, then  7800  B.  t.  u.  will  be  given  to  the  water  per 
pound  of  fuel  burned,  and  the  amount  of  coal  burned  per 
hour  will  be  51789100  -f-  7800  =  6640  pounds.  This  gives 
6640  -f-  1548  =  4.3  pounds  of  fuel  per  boiler  horse  power 
hour,  and  6.7  pounds  of  water  evaporated  per  pound  of  fuel. 
If  the  flue  gases  have  12  per  cent.  CO2,  there  are  being  used 
according  to  experimental  data,  about  21  pounds  of  air  or 
22  pounds  of  the  gases  of  combustion,  per  pound  of  fuel 
burned.  This  is  equivalent  to  6640  X  22  =  146080  pounds  of 
flue  gases  total.  Suppose  now  that  these  gases  leave  the 
furnace  for  the  chimney  at  a  temperature  of  550  degrees 
F.,  that  the  economizer  drops  the  temperature  of  the  gases 
down  to  350  degrees  (a  condition  which  is  very  reasonable) 
and  that  the  specific  heat  of  the  gases  is  about  .22,  we  have 
146080  X  .22  X  (550  —  350)  =  6427520  B.  t.  u.  given  off  from 
the  gases  per  hour  in  passing  through  the  economizer  (see 
numerator  in  formula  99).  This  heat  is  taken  up  by  the 
circulating  water  in  passing  through  the  economizer  to- 
ward the  outgoing  main.  Now  if  the  water,  as  it  returns 
from  the  circulating  system,  enters  the  economizer  at  155 
degrees,  and  leaves  at  180  degrees,  we  will  have  6427520 
-T-  (180  —  155)  =  257100  pounds  of  water  heated  per  hour. 
This  is  equivalent  to  supplying  257100  -f-  8.33  =  30864  square 
feet  of  radiation  per  hour  when  the  plant  is  running  at 
its  peak  load.  Taking  the  "pounds  of  steam  per  hour"  in 
the  above  as  the  only  variable  quantity,  we  are  fairly  safe 
in  saying  that  the  heat  in  the  chimney  gases  from  one  horse 
power  of  steaming  boiler  service  will  supply,  through  an 
economizer,  30864  -T-  1548  =  20  square  feet  of  radiation  in  the 
district.  In  plants  where  only  7  pounds  of  water  is  allowed 
to  each  square  foot  of  radiation  per  hour,  this  becomes  23.8 
square  feet  of  radiation  instead. 

165.  Square  Feet  of  Economizer  Surface  Required  to 
Heat  the  Circulating  Water  In  Art.  164: — Let  K  =  the  coeffi- 
cient of  heat  transmission  through  clean  cast  iron  tubes  and 
E  —  the  efficiency  of  the  tube  surface  when  in  average  serv- 


DISTRICT  HEATING  227 

Ice,  also,   let  the  terms   for   the  temperatures   of  the   gases 
and  the  circulating  water  be  as  given  in  Art.  164,  then 

Heat  trans,  per  hour  from  gases  to  water 


/    tb  +  ta        tf  +  tw    \ 

KXEXl ) 

V          2  27 


(100) 


This  formula  assumes  that  the  rate  of  heat  flow  through 
the  tubes  is  the  same  at  all  points.  As  a  matter  of  fact  this 
rate  changes  slightly  as  the  water  becomes  heated,  but 
the  error  is  not  worth  mentioning  in  such  a  formula,  where 
the  efficiency  of  the  surface  may  be  anything  from  100  per 
cent,  in  new  tubes,  to  as  low  as  30  or  40  per  cent,  for  old 
ones. 

APPLICATION.  —  Let  K  =  1  and  E  =  .4,  then 

6427520 
.Re  =  -  =  8125   sq.  ft. 

/  550  +  350  180  +  155 

7X  .4  X 


2  2 

With  12  square  feet  of  surface  per  tube  this  gives  677  tubes. 

166.  Square  Feet  of  Economizer  Surface  to  Install  when 
the  Economizer  is  to  be  Used  to  Heat  the  Feed  Water  for 
the  Steaming  Boilers: — If  30  pounds  of  feed  water  are  fed 
to  the  boiler  per  horse  power  hour,  and  if  K  =  7,  E  =  .4, 
tb  =  550,  ts  =  350,  tf  =  250,  and  tw  =  90  (about  the  lowest 
temperature  at  which  water  should  enter  the  economizer), 
then  the  square  feet  of  surface  per  horse  power  is 

30  X  (250  —  90) 
Re  =  =  6.1  sq.  ft. 

550  +  350  250  +  90  \ 


7  X  .4  X 


2  2  / 

167.  Total  Capacity  of  the  Boiler  Plant  and  the  Number 
of  Boilers  Installed: — The  following  discussion  on  the  size 
of  the  boiler  plant  is  purely  for  illustrative  purposes  and 
is  intended  to  show  how  such  problems  may  be  analyzed. 
In  most  cases  the  exhaust  steam,  and  the  economizer  if  used, 
will  fall  far  short  of  supplying  the  total  radiation  in  the 
district,  especially  when  the  electrical  output  is  light  and 
the  weather  is  cold.  Suppose  it  be  desired  to  install  extra 
boilers  to  be  used  as  heaters  for  the  radiation  not  supplied 
from  these  two  sources.  To  determine  the  amount  of  ex- 
tra boilers,  find  the  amount  of  radiation  to  be  supplied  by 


228  HEATING  AND  VENTILATION 

the  exhaust  steam  and  the  economizer  and  subtract  this 
from  the  total  radiation.  The  difference  must  be  supplied 
by  boilers  used  as  heaters.  It  is  probably  not  safe  to  esti- 
mate too  closely  on  the  amount  of  exhaust  steam  given  to 
the  heating  system.  The  maximum  amount  of  44500  pounds 
per  hour  was  obtained,  in  this  case,  by  pumping  one  gal- 
lon of  water  per  hour  for  each  square  foot  of  radiation  and 
by  pumping  city  water,  in  addition  to  that  obtained  from 
the  engines.  In  heating,  a  less  amount  of  water  than  this 
may  be  circulated  even  on  the  coldest  day.  This  is  -possi- 
ble, first,  because  water  may  be  carried  at  a  higher  tem- 
perature than  that  stated,  and  second,  because  there  may 
be  less  loss  of  heat  in  the  conduit,  thus  giving  more  heat  per 
gallon  of  water  to  the  radiation.  Again,  in  estimating  for 
a  city  water  supply,  the  demands  are  not  very  constant  and 
are  difficult  to  estimate.  In  this  one  design  it  was  thought 
that  44500  pounds  per  hour  was  a  very  liberal  allowance 
and  could  be  dropped  to  35000  pounds  (140000  square  feet 
of  radiation),  when  estimating  the  amount  of  radiation 
supplied  by  the  exhaust  steam. 

By  Fig.  94  it  will  be  seen  that  the  minimum  load  on  the 
steaming  boilers  carries  through  six  hours  out  of  the  entire 
twenty-four  and  that  the  exhaust  steam  at  this  time  drops 
to  22890  pounds  per  hour,  supplying  91560  square  feet  of 
radiation.  This  minimum  load  is  51  per  cent,  of  the  max- 
imum, and  66  per  cent,  of  the  amount  taken  as  an  average 
i.  e.,  35000.  The  work  done  by  the  economizer  is  fairly  con- 
stant, since  the  amount  of  economizer  surface  lost  by  the 
steaming  boilers  under  minimum  load  would  be  made  up 
t>y  the  additional  heating  boilers  thrown  into  service.  On 
the  basis  of  35000  pounds  per  hour,  the  exhaust  steam  and  the 
stack  gases  together  would  heat  170960  square  feet  and 
there  would  be  left  13540  square  feet  (184500  —  20  X  1548 
—  4  X  35000),  to  be  heated  by  additional  boilers.  Under 
minimum  load  this  would  be  approximately  122500,  leaving 
62000  square  feet  to  be  heated  by  additional  boilers.  If  one 
boiler  horse  power  will  supply  160  square  feet  of  radiation, 
then  it  would  require  84  and  387  boiler  horse  power  re- 
spectively to  supply  the  deficiency  and  the  total  horse  power 
needed  in  each  case  would  be  1632  and  1935.  A  more  satis- 
factory analysis,  however,  is  the  following  which  is  worked 
on  the  lasis  of  44500  pounds  per  hour. 


DISTRICT  HEATING  229 

Let  Ws  =  total  number  of  pounds  of  steam  used  in  the 
plant  per  hour  =  approximate  number  of  pounds  of  exhaust 
steam  available  for  heating  the  circulating  water  per  hour; 
We  =  equivalent  number  of  pounds  of  steam  evaporated  froir> 
and  at  212°;  \  =  total  heat,  above  32°,  in  one  pound  of  dry 
steam  at  the  boiler  pressure;  q1  =  total  heat,  above  32°,  in 
one  pound  of  feed  water  entering  the  boiler;  then,  if  the 
latent  heat  of  steam  at  atmospheric  pressure  =  969.7  B.  t.  u., 
we  have 

W*  (A  —  a1  ) 

We  = (101) 

969.7 

and  the  corresponding  boiler  horse  power  needed  as  steam' 
ing  boilers  will  be 

We 

BS  H.  P.  = (102) 

34.5 

Next,  the  radiation  in  the  district  that  can  be  supplied 
by  the  exhaust  steam  is  Rw  =  4  Ws,  and  the  amount  sup- 
plied by  the  economizer  is  Re  =  20  X  B.  H.  P.  From  which 
we  may  obtain  the  capacity  of  the  heating  boilers  as, 

Total  Radiation  —  4  Ws  —  20  B.  H.  P. 

Bw  H.  P.  = (103) 

160 

The  total  boiler  horse  power  of  the  plant  is,  therefore,  the 
sum  of  Bs  H.  P.  and  Bw  H.  P.  To  obtain  formula  103  for  any 
specific  case  one  must  consider  the  maximum  and  minimum 
conditions  of  the  steaming  boiler  plant.  Let  Ws  (max)  — 
maximum  exhaust  steam,  and  Ws  (min)  =  minimum  exhaust 
steam.  Then  for  the  two  following  conditions  we  will  have, 
Case  1,  where  the  steaming  and  heating  boilers  are  independent  of 
each  other,  the  total  boiler  horse  power  installed  ==  Bs  H.  P. 
+  [total  radiation  —  4  Ws  (min)  —  20  X  7?.  H.  P.  in  use]  + 
160;  Also,  Case  2,  where  a  part  or  all  of  the  steaming  boilers  are 
piped  for  loth  steaming  and  water  service,  the  total  boiler  horse 
power  installed  =  Bs  H.  P.  +  [total  radiation  —  4  Ws  (max) 
—  20  X  B.  H.  P.  in  use]  -j-  160.  It  will  be  noticed  that  the  last 
term  representing  the  economizer  service  is  simply  stated 
as  boiler  horse  power  and  no  distinction  is  made  between 
steaming  or  heating  service.  This  term  will  be  difficult  to 
estimate  to  an  exact  figure  because  it  should  be  the  total 
horse  power  in  use  at  any  one  time,  both  steaming  and  heat- 
ing, and  this  can  only  be  obtained  by  approximation.  It 
makes  no  difference  what  service  the  boiler  may  be  used  for, 
the  work  of  the  economizer  would  be  practically  the  same. 


230  HEATING  AND  VENTILATION 

Probably  the  most  satisfactory  way  is  to  substitute  the  value 
Ba  H.  P.  for  B.  H.  P.  in  the  economizer  and  get  the  approxi- 
mate total  horse  power,  then  if  this  approximate  total  horse 
power  differs  very  much  from  that  actually  needed,  other 
trials  may  be  made  and  new  values  for  the  total  horse  power 
obtained  until  the  equation  is  satisfied. 

Application. — Let  Ws  =  pounds  of  exhaust  steam,  ^  = 
1191.8  (125  pounds  gage  pressure),  and  q'  =  28  (feed  water 
at  60°);  then  when  WB  =  44500 

We  =  53400 

Bs  H.  P.  =  1548 

184500  —  4  X  22890  —  20  X  1548 

Bw  H.  P.   Case    1  =  =   387 

160 
184500  —  4  X  44500  —  20  X  1548 

Bw  H.  P.  Case  2  =  =  —153 

160 

This  shows  that  there  is  an  excess  of  waste  heat  in  Case  2, 
making  a  total  boiler  horse  power,  Case  1,  =  1935  and  Case 
2,  =  1548.  Investigating  Case  1  to  see  what  error  was  intro- 
duced by  using  1548  in  the  economizer,  we  find  approximately 
800  horse  power  of  steam  boilers  in  use,  and  the  total  horse 
power  to  be  1187,  which  is  about  360  horse  power  on  the 
unsafe  side.  Substitute  again  and  check  results.  Case  2  is 
reasonably  close.  In  any  case  the  most  economical  size  of 
boiler  plant  to  install  in  a  plant  requiring  both  steaming  and 
heating  boilers  is  one  where  at  least  a  part,  if  not  all,  of  the 
boilers  are  piped  so  as  to  be  easily  changed  from  one  system 
to  the  other.  By  such  an  arrangement  the  capacity  may  be 
made  the  smallest  possible.  After  obtaining  the  theoretical 
size  of  the  plant,  it  would  be  well  to  allow  a  small  margin 
in  excess  so  that  one  or  two  boilers  may  be  thrown  out  of 
commission  for  repairs  and  cleaning  without  interfering 
with  the  working  of  the  plant.  Case  2  seems  to  be  the  better 
arrangement.  Assuming  1800  total  boiler  horse  power  we 
might  very  well  put  in  six  300  H.  P.  boilers  arranged  in  three 
batteries. 

168.  Cost  of  Heating  from  a  Central  Station  (Direct  Fir- 
ing): — It  will  be  'Of  interest  in  this  connection  to  estimate 
approximately  the  cost  in  supplying  heat  by  direct  firing  to 
one  square  foot  of  hot  water  radiation  per  year  from  the 
average  central  station.  In  doing  this  make  the  boiler  as- 
sumptions to  be  the  same  as  Art.  163.  Take  coal  at  13000 


DISTRICT  HEATING 


231 


Fig. 
Power  Plant  Layout. 


232  HEATIXG  AXD  VEXTILATIOX 

R.  t.   u-   per  pound,   2000  pounds   per   ton,   and  a  boiler  effi- 

ciency of  €0  per  cent.  "Water  enters  the  boiler  at  155  degrees 
from  the  returns,  and  is  delivered  to  the  mains  at  180  de- 
grees. From  the  value  of  the  coal  as  stated,  we  would  have 
15*0£000  B.  t.  u.  per  ton  given  off  to  the  water.  This  is 

equivalent  to  h  eating-  €24000  pounds,  or  74&10  gallons,  of 
water.  If  one  ton  of  coal  costs  $2.00  at  the  plant,  we  have 

200  -j-   74S10  =    .0027  cents 

This  represents  the  amount  paid  to  reheat  one"  gallon  of 
water,  or  to  supply  one  s-quare  foot  of  heading  surface  one 
tour  at  an  outside  temperature  of  zero  degrees.  Take  the 
average  temperature  for  the  seven  cold  months  at  32  de- 
grees. This  is  the  average  for  the  coldest  year  in  the  twenty 
years  preceding  1&10.  as  recorded  at  the  U.  S.  Exp.  Station, 
LaFayette.  Indiana.  "We  then  have  an  average  difference 
between  the  inside  and  the  outside  temperatures  in  any 
residence  of  7t  —  32  =  2S.  This  makes  the  formula  for 
the  heat  loss.  Art.  2*,  reduce  to  3S  -E-  70  =  .54  of  its 
former  value.  Now,  if  it  takes  one  gallon  of  water  per 
square  foot  of  radiation  per  hour  under  maximum  conditions, 
we  have  for  the  seven  months  .54  X  !  X  Zb  S.  24  =  2722  gal- 
lons of  water  needed  for  each  square  foot  of  radiation  per 
each  healing  year.  This  is  equivalent  to  2722  y  .0027  =  7.35 
cents  per  square  foot  of  radiation  for  the  heating  year  of 
seren  months. 

When  the  plant  is  working  under  the  best  conditions 
this  figure  should  be  reduced.  It  tian  be  done  with  boilers 
of  a  higher  eJideaey  than  that  stated,  and  it  can  be  done 
by  using  a  cheaper  coal,  both  of  which  are  possible  in  many 


1C*.  Cwrt  of  Hratfms  from  a  Oatral  Station, 
•f  Tests:  —  The  following  tests  were  conducted  upon  the 
Merchants  R^atfng  and  Lighting  Plant,  LaFayette,  Ind.;  one 
in  19M  and  the  other  in  1M8.  The  plant  was  changed  slight- 
ly between  the  two  tests  and  the  radiation  carried  upon  the 
liaes  was  much  increased,  although  tm  all  essential  features 
the  pHsit  was  the  Miar.  The  circulating  water  was  heated 
by  rmhsast  steam  beaters  and  by  heating  boilers. 

The  plant  had  the  following  important  pieces  of  appara- 
tus  employed  hi  grarisliag  or  absorbing  the  heat  supply: 


DISTRICT  HEATING  233 

BOILERS  (Steaming  and  Heating). 

Two  125  11.  P.  Stirling  boilers.  Total  heating  surface 
2524  sq.  ft. 

Three  250  H.  P.  Stirling  boilers.  Total  heating  surface 
7572  sq.  ft. 

Pressure  on  steaming  boilers   (gage),   150  Ibs. 

Pressure  on  heating  boilers   (approx.),   60  Ibs. 

ENGINES. 

One  450  H.  P.  Hamilton  Corliss  comp.  engine,  direct  con- 
nected to  a  300  K.  W.  Western  Electric  72-pole  alternating 
current  generator  120  R.  P.  If.  This  engine  carried  the  load 
of  the  plant  when  it  was  above  50  K.  W.,  which  was  generally 
from  5:30  A.  M.  to  11:30  P.  M.  When  this  unit  was  run,  direct 
current  was  obtained  by  passing  the  alternating  current 
through  a  motor  generator  set. 

One  125  H.  P.  Westinghouse  comp.  engine,  belted  to  one 
75  K.  W.  3-phase  alternating  and  two  direct  current  genera- 
tors, and  run  at  312  R.  P.  M,  This  unit  was  generally  run 
between  11:30  P.  M.  and  5:30  A.  ivi. 

One  250  H.  P.  Westinghouse  comp.  engine,  belt  connected 
to  a  200  K.  W.  generator  and  two  smaller  machines. 

PUMPS. 

One  centrifugal,  two-stage  pump,  Dayton  Hydraulic  Co., 
direct  connected  to  a  Bates  vertical  high  speed  engine  at  300 
R.  P.  M. 

Two  Smith-Vaile  horizontal  recip.  duplex  pumps  14  in. 
X  12  in.  X  18  in.  Each  of  the  three  pumps  connected  to  the 
return  main  in  such  a  way  as  to  be  able  to  use  any  combina- 
tion at  any  one  time  to  circulate  the  water.  The  centrifugal 
pump  had  been  in  service  only  one  season.  It  had  a  capacity 
about  equal  to  the  two  reciprocating  pumps  and  under  the 
heaviest  service  this  pump  and  one  of  the  duplex  pumps 
were  run  in  parallel. 

One  Smith-Vaile  horizontal  reciprocating  tank  pump 
6  in.  X  4  in.  X  6  in.  to  lift  the  water  of  condensation  from 
the  exhaust  heater  to  the  tank. 

One  Smith-Vaile  horizontal  reciprocating  make-up  pump 
6  in.  X  4  in.  X  6  in.  to  replace  the  water  that  was  lost  from 
the  system. 


234 


HEATING  AND  VENTILATION 


Two  National  horizontal  reciprocating  boiler  feed  pumps. 

One  9%  in.  Westinghouse  air  pump,  to  keep  up  the  supply 
of  air  through  the  conduits  to  the  regulator  system  in  the 
heated  buildings. 

One  Deane  vertical  deep  well  pump,  to  deliver  fresh 
water  to  the  supply  tank. 

One  Baragwanath  exhaust  steam  heater  or  condenser, 
having  1000  sq.  ft.  of  heating  surface. 


PARTIAL  SUMMARY  OF  RESULTS. 

1906 

1.  Square  feet  of  radiation 118000 

2.  Temperature  of  circulating  water  in 
degrees   F.-,   flow  main 158.36 

3.  Temperature  of  circulating  water  in 
degrees  P.,   return  main 139.9 

4.  Temperature  of  circulating  water  in 
degrees  F.,   after  leaving  heater 145.6 

5.  Temperature    of    outside    air    in    de- 
grees   F 32.6 

6.  Temperature   of   stack   gases   in   de- 
grees F.,   steaming  boiler 

7.  Temperature   of   stack   gases   in   de- 
grees  F.,   heating  boiler 562. 

8.  Draft  in  stacks  (all  boilers  averaged) 

in  inches  of  water .  68£ 

9.  Heating    value    of    coal    in    B.    t.    u. 

per  pound 12800 

10.  B.  t.  u.  delivered  to  steaming  boiler 

per  hour  by  coal .18187000 

11.  B.  t.  u.  delivered  to  heating  boilers 

per  hour  by  coal 19226000 

12.  B.  t.  u.  delivered  to  circulating  water 

by  heating  boilers  per  hour 11800000 

13.  B.  t.  u.  to  be  charged  to  heating  boil- 
ers (Item  12 — Item  15) 7650000 

14.  B.  t.  u.  delivered  to  circulating  water 
by   exhaust   steam  from   tne   gener- 
ating engines  per  hour 3600000 


1908 
150000 


DISTRICT  HEATING 


235 


15.  B.    t.    u.    thrown    away    during    test 
from    pump    exhausts    and    available 

for  heating- circulating  water 4150000         8471000 

16.  B.  t.  u.  available  for  heating-  circu- 
lating water  from  all  exhaust  steam 
as    in    normal    running    (Item    14    + 

Item    15) 7750000       15073000 

17.  Total    B.    t.    u.    given   to    circulating 

water  per  hour  (Item  13  +  Item  16)  .  .15400000       22007000 

18.  Gallons   of   water   pumped   per   hour 

[Item  17  —  (8.33  X  Items  2-3)] 100000  108000 

19.  Gallons  of  water  pumped  per  square 
foot  of  radiation  per  hour  (Item  18 

-^  Item  1) .85  .70 

20.  Efficiency    of    heating    boilers    (Item 

12  -~  Item  11)   approx .60  .55 

21.  Value  of  the  coal  in  cents  per  ton  of 

2000  pounds  at  the  plant 200.  175. 

22.  Average  electrical  horse  power 68  141 

Note. — The  above  values  are  averages  and  were  taken 
for  each  entire  test.  The  B.  t.  u.  values  were  considered  sat- 
isfactory when  approximated  to  the  nearest  thousand. 

170.  Regulation: — The  regulation  of  the  heat  within  the 
residences  is  best  controlled  from  the  power  plant.  In  most 
heating  plants  a  schedule  is  posted  at  the  power  house  which 
tells  the  engineer  the  necessary  temperature  of  the  circu- 
lating water  to  keep  the  interior  of  the  residences  at  70 
degrees  with  any  given  outside  temperature.  In  other  heat- 
ing plants  the  regulation  is  by  means  of  air  carried  from  the 
compressor  at  the  power  house  through  a  main  running 
parallel  with  the  water  mains  in  the  conduits  and  branching 
to  each  building  where  it  is  used  under  a  pressure  of  15 
pounds  to  operate  thermostats,  which  in  turn  control  the 
water  inlets  to  the  radiators.  A  closer  regulation  is  ob- 
tained in  the  latter  system  than  in  the  former,  but  it  is 
needless  to  say  that  the  thermostats  require  careful  adjust- 
ments and  frequent  inspections. 


236  HEATING  AND  VENTILATION 

STEAM  SYSTEMS. 

171.  Heating  by  steam  from  a  central  station,  compared 
with  hot  water  heating,  is  a  very  simple  process.  The  power 
plant  equipment  is  composed  of  a  few  inexpensive  parts,  the 
operation  of  which  is  very  simple  and  easily  explained. 
These  parts  have  but  few  points  that  require  rational  de- 
sign. Because  of  the  simplicity  and  because  of  the  similarity 
to  the  preceding  discussion  on  hot  water  systems,  the  work 
on  steam  systems  will  be  very  brief.  All  questions  referring 
to  the  construction  of  the  conduit,  the  supporting  of  the 
pipes,  the  provision  for  contraction  and  expansion,  the  drain- 
ing of  the  pipes  and  the  draining  of  the  conduits,  are  com- 
mon to  both  hot  water  and  steam  systems  and  are  discussed 
in  Arts.  135  and  136.  A  large  part  of  the  work  referring 
directly  to  district  hot  water  heating  applies  with  almost 
equal  force  to  steam  heating.  This  part  of  the  work,  there- 
fore, will  deal  with  such  parts  of  the  power  plant  equipment 
as  differ  from  those  of  the  hot  water  system. 

'Steam  heating  may  be  classified  under  two  general  heads, 
high  pressure  and  low  pressure.  A  very  small  part,  only,  of 
the  heating  in  this  country  is  now  done  by  what  may  be 
strictly  called  high  pressure  service,  i.  e.,  where  radiators  or 
coils  are  under  pressures  from  30  to  60  pounds  gage,  and 
this  small  amount  is  gradually  decreasing.  Ordinarily,  steam 
is  generated  at  high  pressure  at  the  boiler,  60  pounds  to  150 
pounds  gage,  and  reduced  for  line  service  to  pressures  vary- 
ing from  0  to  30  pounds  gage,  with  a  still  further  reduction 
at  the  building  to  pressures  varying  from  0  to  10  pounds 
gage,  for  use  in  radiators  and  coils.  Where  exhaust  steam 
is  used  in  the  main,  the  pressure  is  not  permitted  to  go  higher 
than  10  pounds  gage,  because  of  the  back  pressure  on  the 
engine  piston.  Where  exhaust  steam  is  not  used,  the  pres- 
sures may  go,  as  high  as  30  pounds  gage,  thus  allowing  for  a 
greater  pressure  drop  in  the  line  and  a  corresponding  re- 
duction in  pipe  sizes. 

The    principles    involved    in    the    power    plant    end    of 
a  steam  heating  system  may  be  represented  by  Fig.  100.     It 
will  be  seen  that  the  exhaust  steam  from  the  engines  or  tur- 
bines   has    four   possible    outlets.      Passing    through    the    oil  : 
separator,  which  removes  a  large  part  of  the  entrained  oil,  i 
part  of  the  exhaust  steam  is  turned  into  the  heater  for  use  in  i 


DISTRICT  HEATING 


237 


heating  the  boiler  feed  water.  The  rest  of  the  steam  passes 
on  into  the  heating  system.  If  there  be  more  exhaust  steam 
than  is  necessary  to  supply  the  heating  system,  the  balance 
may  go  to  the  atmosphere  through  the  back  pressure  valve. 
When  the  heating  system  is  not  in  use,  as  would  be  the  case 
in  the  four  warm  months  of  the  year,  the  exhaust  steam  may 
be  passed  into  the  condenser. 


Fig.   100. 


It  is  very  evident,  from  what  has  been  said  before,  that 
it  would  not  be  economical  to  condense  the  steam  in  a  con- 
denser as  long  as  there  is  a  possibility  of  using  it  in  the 
heating  system.  The  increased  gain  in  efficiency,  when  con- 
densing the  exhaust  steam  under  vacuum,  is  very  small  com- 
pared to  the  gain  when  this  same  steam  is  used  for  heating 
purposes.  It  would  also  be  very  poor  economy  to  use  any  live 
steam  for  heating  when  there  were  any  exhaust  steam 
wasted.  When  the  amount  of  exhaust  steam  is  insufficient, 
live  steam  is  admitted  through  a  pressure  reducing  valve. 

172.     Drop  in  Pressure  and  the  Diameter  of  the  Mains: — 

The  flow  of  steam  in  a  pipe  follows  the  same  general  laws  as 
the  flow  of  water.  The  loss  of  head  may  be  represented 
by  the  well  known  formula 

Jif  =  (104) 

9d 

where  hf  =  loss  of  head  in  feet,  <£  =  coefficient  of  friction, 
v  =  velocity  in  feet  per  second,  I  —  length  of  pipe  in  feet, 


238  HEATING  AND  VENTILATION 

d  =  diameter  of  the  pipe  in  feet  and  g  =  32.2.  Substitute,  hi  = 
144  p  -+-  D,  where  p  =  drop  in  pressure  in  pounds  and  D  =  den- 
sity of  the  steam,  and  find 

2  </>  lv2 

P  =  (105) 

144  gd 

The  coefficient  of  friction  is  found  to  vary  with  the  velocity  of 
the  steam  and  with  the  diameter  of  the  pipe.  Prof.  Unwin 
found,  that  for  velocities  of  100  feet  per  second  (good  prac- 
tice for  transmission  lines),  it  could  be  expressed  as  follows, 
where  c  is  a  constant  to  be  found  by  experiment, 

-\ ) 

10  d    ) 
which,  when  substituted  in  (105),  gives 


lv2Dc 

72  gd 

Let  TF  =  pounds  of  steam  passing  per  minute  and  efi  =  diam- 
eter of  pipe  in  inches,  then 


,  =  -_(»  +  —  i  ace, 


1          /  3.6      \       W2lc 

P  = (    1  H ) (107) 

20.663  \  di     /        d^D 

From  this  formula  we  may  obtain  any  one  of  the  three  terms, 
W,  d^  or  p,  if  the  other  two  are  known.  Table  31,  Appendix, 
was  compiled  from  (107)  with  c  =  .0027.  For  discussion,  see 
Trans.  A.  S.  M.  E.,  Vol.  XX,  page  342,  by  Prof.  R.  C.  Carpen- 
ter. Also  Encyclopedia  Britannica,  Vol.  XII,  page  491.  See 
also,  Kent,  page  670,  and  Carpenter's  H.  •&  V.  B.,  page  51. 

It  will  be  seen  that  Table  31  is  compiled  upon  the  basis 
of  one  pound  pressure  drop,  at  an  average  pressure  of  100 
pounds  absolute  in  the  pipe.  Since,  in  any  case,  the  drop 
In  pressure  is  proportional  to  the  square  of  the  pounds  of 
steam  delivered  per  minute  (other  terms  remaining  constant), 
the  amount  delivered  at  any  other  pressure  drop  than  that 
given  (one  pound)  would  be  found  by  multiplying  the  amount 
given  in  the  table  by  the  square  root  of  the  desired  pressure 
drop  in  pounds.  Also,  since  the  weight  of  steam  moved  at 
the  same  velocity,  under  any  other  absolute  pressure,  is  ap- 
proximately proportional  to  the  absolute  pressures  (other 
terms  remaining  constant),  we  have  the  amount  of  steam 
moved  under  the  given  pressure,  found  by  multiplying  the 
amount  given  in  the  table  by  the  square  root  of  the  ratio  of 
the  absolute  pressures.  To  illustrate  the  use  of  the  table — 


DISTRICT  HEATING  239 

suppose  the  pressure  drop  in  a  1000  foot  run  of  6  inch  pipe 
is  8  ounces,  when  the  average  pressure  within  the  pipe  is  10 
pounds  gage.  The  amount  of  steam  carried  per  minute  is 
93.7  X  V^5  -r  V100  -T-  25  =  133  pounds.  Or,  if  the  drop  is  4 
pounds,  at  an  average  inside  pressure  of  50  pounds  gage, 
the  amount  carried  would  be  150  pounds  per  minute.  Con- 
versely— find  the  diameter  of  a  pipe,  1000  feet  long,  to  carry 
150  pounds  of  steam  pe.r  minute,  at  an  average  pressure 
of  10  pounds  gage  and  a  pressure  drop  of  8  ounces. 

150  JfTHT" 

W  (table)  =  — —  X  J =  264  pounds 

V.5  ^     65 

which,  according  to  the  table,  gives  a  9  inch  pipe. 

173.  Dripping:   the    Condensation  from  the    Mains: — The 

condensation  of  the  steam,  which  takes  place  in  the  con- 
duit mains,  should  be  dripped  to  the  sewer  or  the  return 
at  certain  specified  points,  through  some  form  of  steam 
trap.  These  traps  should  be  kept  in  first  class  condition. 
They  should  be  inspected  every  seven  or  ten  days.  No  pipe 
should  be  drilled  and  tapped  for  this  water  drip.  The  only 
satisfactory  way  is  to  cut  the  pipe  and  insert  a  tee  with 
the  branch  looking  downward  and  leading  to  the  trap.  The 
sizes  of  the  traps  and  the  distances  between  them  can  only  be 
determined  when  the  pounds  of  condensation  per  running 
foot  of  pipe  can  be  estimated. 

174.  Adaptation  to  Private  Plants: — District  steam  heat- 
ing systems  may  be  adapted  to  private  hot  water  plants  by 
the  use  of  a  "transformer."     This  in  principle  is  a  hot  water 
tube  heater  which  takes  the  place   of  the  hot  water  heater 
of  the  system.     It  may  also  be  adapted  to  warm  air  systems 
by  putting  the  steam  through  indirect  coils  and  taking  the 
air  supply  from  over  the  coils. 

175.  General    Application  to    the    Typical    Design: — The 

following  brief  applications  are  meant  to  be  suggestive  of  the 
method  only  and  the  discussions  of  the  various  points  are 
omitted. 

Square  feet  of  radiation  in  the  district. — 

R8  =  184500  X  170  4-  255  =  123000  square  feet. 

Amount  of  heat  needed  in  the  district  to  supply  the  radiation  for 
one  hour  in  zero  weather. — • 

Total  heat  per  hour  =  123000  X  255  =  31365000  B.  t.  u. 


240  HEATING  AND  VENTILATION 

Amount  of  heat  necessary  at  the  power  plant  to  supply  the  radiation 
for  one  hour  in  zero  weather. — Assuming  15  per  cent,  heat  loss  in 
the  conduit  (this  is  slightly  less  than  that  allowed  for  the 
hot  water  two-pipe  system,  20  per  cent.),  we  have, 
31365000  -=-  .85  =  36900000  B.  t.  u.  per  hour. 

Total  exhaust  steam  available  for  heating  purposes. — 
1FS  (max)  =  (23100  +  8680)   X  1.15  —  36547  pounds  per  hour. 
Ws   (min)  =  (    1490  -f  8680)   X  1.15  =  11696  pounds  per  hour. 

Total  B.  t.  u.  available  from  exhaust  steam  per  hour  for  heating. — 
Let  the  average  pressure  in  the  line  be  5  pounds  gage  and 
let  the  water  of  condensation  leave  the  indirect  coils  in  the 
residences  at  140  degrees.  We  then  have  from  one  pound  of 
exhaust  steam,  by  formula  75, 

B.  t.  u.  =  .85  X  960  +  195.6  —  (140  —  32)  —  903.7 
Assuming  this  to  be  900  B.  t.  u.  per  pound,  the  total  available 
heat  from  the  exhaust  steam  for  use  in  the  heating  system  is, 
maximum  total  =  32892300  B.  t.  u.  and  the  minimum  total  — 
10526iOn  B.   t.   u. 

Square  feet  of  steam  radiation  that  can  be  supplied  by  one  pound 
of  exhaust  steam  at  5  pounds  gage. — 

tfs  =  900  -r-  (255  -f-    .85)   =  3. 

Total  B.  t.  u.  to  be  supplied  by  live  steam. — 

B.  t.  u.   (max  load)  =  36900000  —  32892300  =  4007700  B.  t.  u. 
B.  t.  u.   (min.  load)  =  36900000  —  10526400  =  26373600  B.  t.  u. 

Total  pounds  of  live  steam  necessary  to  supplement  the  exhaust 
steam. — Let  the  steam  be  generated  in  the  boiler  at  125 
pounds  gage.  With  feed  water  at  60  degrees 

Max.   load  =     4007700  -j-  1163.8  =     3444  pounds. 
Min.    load  =   26373600   -j-   1163.8   =   22661   pounds. 

Boiler  horse  power  needed  for  the  steam  power  units. — As  in 
Arts.  164  and  167, 

Bs  H.  P.  (max.)  =  36547  X  1.2  -=-  34.5  =  1271. 
Bs  H.  P.   (min.)  =  11696  X  1.2  -r-  34.5  =  407. 

Total  "boiler  horse  power  needed  in  the  plant. — Maximum  load. 
B.  H.  P.  (total)  —  1271  +  (3444  X  1.2  4-  34.5)  =  1391. 

It  will  be  noticed  that  this  total  horse  power  is  157  horse 
power  less  than  the  corresponding  Case  2  in  Art.  167.  This 
is  accounted  for  by  the  fact  that  no  steam  is  used  up  in  work 
in  the  circulating  pumps,  also  that  the  conditions  of  steam 
generation  and  circulation  are  slightly  different.  1500  boiler 
horse  power  would  probably  be  installed  in  this  case. 


DISTRICT  HEATING 


241 


Size  of  Conduit  Mains.— Let  it  be  required  to  find  the 
diameters  of  the  mains  system  in  Jig.  96  at  the  important 
points  shown.  Art.  144  gives  the  length  of  the  mains  in  each 
part.  Allow  .3  pound  of  steam  for  each  square  foot  of  steam 
radiation  per  hour  (this  will  no  doubt  be  sufficient  to  supply 
the  radiation  and  conduit  losses).  Try,  first,  that  part  of  the 
line  between  the  power  plant  and  A,  with  an  average  steam 
pressure  in  the  lines  of  about  5  pounds  gage  and  a  drop  in 
pressure  of  iy2  ounce  per  each  100  feet  of  run  (approximately 
5  pounds  per  mile).  25200  pounds  per  hour  gives  TF  =  420. 
The  length  of  this  part  of  the  line  is  200  feet  and  the  drop 
is  3  ounces,  or  .19  pound. 


TF  (table)  = 


420  / 

/J9-X    V 


100 


V  . 


=  2158  pounds 


which  gives  a  15  inch  pipe. 

Following   out  the   same 
line,  we  have 

TABLE    XXVIII. 


reasoning  for  all   parts   of  the 


PPtoA 

AtoB 

BtoC 

CtoD 

DtoE 

Distance  between  points      _    

200 

500 

1500 

1500 

500 

Radiation  supplied,  sq.  ft  -  

84000 

57000 

34000 

19000 

8000 

Pressure-drop  in  pounds  =  p  

.19 

.47 

1.4 

1.4 

.47 

Diameter  of  pipe  in  inches,  by  table— 

15 

13 

11 

9 

5 

In  general  practice,  these  values  would  probably  be  taken 
16,  14,  12,  10  and  6  inches  respectively.  Look  up  Table  30, 
Appendix,  and  check  the  above  figures. 


242  HEATING  AND  VENTILATION 


REFERENCES. 

References    on    District    Heating. 

TECHNICAL  BOOKS. 

Allen,  Notes  on  Heating  and  Ventilation,  p.  131. 
TECHNICAL  PERIODICALS. 

Engineering  Netcs.  Comparison  of  Costs  of  Forced-Circula- 
tion Hot  Water  and  Vacuum-Steam  Systems,  J.  T.  Maguire, 
Dec.  23,  1909,  p.  692.  Design  of  Hot-Water  System  with 
Forced-Circulation,  J.  T.  Maguire,  fc>ept.  2,  1909,  p.  247.  En- 
gineering Review.  Determining  Depreciation  of  Underground 
Heating  Pipes,  W.  A.  Knight,  Jan.  1910,  p.  85.  Some  Remarks 
on  District  Steam  Heating,  W.  J.  Kline,  April  1910,  p.  61. 
Toledo  Yaryan  System,  A.  C.  Rogers,  May  1910,  p.  58.  Some 
of  the  Factors  that  Affect  the  Cost  of  Generating  and  Dis- 
tributing Steam  for  Heating.  C.  R.  Bishop,  Aug.  1910,  p.  56. 
Central  Station  Heating  Plant  at  Crawf ordsville,  Ind.,  B.  T. 
Gifford,  Dec.  1909,  p.  42.  Wilkesbarre  Heat,  Light  and  Motor 
Co.,  A  Live  Steam  Heating  Plant,  J.  A.  White,  July  1908,  p.  32. 
The  Heating  and  Ventilating  Magazine.  Schott  Systems  of  Central 
Station  Heating,  J.  C.  Hornung,  Nov.  1908,  p.  19.  Data  on 
Central  Heating  Stations,  Nov.  1909,  p.  7.  Cost  of  Heat  from 
Central  Plants,  March  1909,  p.  31.  Steam  Heating  in  Con- 
nection with  Central  Stations,  Paul  Mueller,  Oct.  1909,  p.  24; 
Nov.  1909,  p.  1.  A  Modern  Central  Hot  Water  Heating  Sta- 
tion, W.  A.  Wolls,  July  1910,  p.  15.  Central  Station  Heating, 
F.  H.  Stevens,  June  1910,  p.  5.  Domestic  Engineering.  Report 
of  Second  Annual  Convention  of  the  National  District  Heating 
Association  at  Toledo,  O.,  June  1,  1910.  Vol.  51,  No.  11,  June 
11,  1910,  p.  255. 


CHAPTER  XIV. 


TEMPERATURE  CONTROL  IN  HEATING  SYSTEMS. 


176.  From  tests   that   have   been   conducted   on   heating 
systems,   it   has  been  conclusively  proven  that  there  is  less 
loss  of  heat  from  buildings  supplied  by  automatic  tempera- 
ture control,  than  from  buildings  where  there  is  no  such  con- 
trol.    A  uniform  temperature   within  the   building   is   desir- 
able from  all  view-points.     Where  heating  systems  are  oper- 
ated, even  under  the  best  of  conditions,  without  such  control, 
the  efficiency  of  the  system  would  be  increased  by  its  appli- 
cation.    No  definite  statement  can  be  made  for  the  amount  of 
heat  saved,  but  it  is  safe  to  say  that  it  is  between  5  and  20 
per    cent.      A    building    uniformly    heated    during    the    entire 
time,   requires  less  heat  than  if  a  certain  part  or  all  of  the 
building    were    occasionally    allowed    to    cool    off.      When    a 
building  falls  below  normal  temperature  it  requires  an  extra 
amount  of  heat  to  bring  it  up  to  normal,  and  when  the  inside 
temperature  rises  above  the  normal,  it  is  usually  lowered  by 
opening  windows  and  doors  to  enable  the  heat  to  leave  rap- 
idly.    High  inside  temperatures  also  cause  a  correspondingly 
increased  radiation  loss.    E  luctuations  of  temperature,  there- 
fore,  are   not  only  undesirable   for   the   occupants,   but  they 
are   very   expensive   as   well. 

177.  Principles  of  the  System: — Temperature  control  may 
be    divided    into    two    general    classifications, — small    plants 
and  large  plants.     The  control  for  small  plants,  i.  e.,  such  plants 
as  contain  very  few  heating  units,  is  accomplished  by  regu- 
lating the  drafts  by  special  dampers  at  the  combustion  cham- 
ber.    This  method  controls  merely  the  process  of  combustion 
and  has  no  especial  connection  with  individual  registers   or 
radiators,  it  being  assumed  that  a  rise  or  fall  of  temperature 
in    one    room    is    followed    by    a    corresponding    effect    in    all 
the  other  rooms.     This  method  assumes  that  all  the  heating 
units    are    very    accurately    proportioned    to    the    respective 
rooms.      The    dampers    are    operated    through    a    system    of 
levers,  which  system  in  turn  is  controlled  by  a  thermostat. 
Fig.    101    shows   a   typical     application     of    such     regulation. 


244 


HEATING  AND  VENTILATION 


Fig.   101. 


This  may  be  applied  to 
any  system  of  heat.  In 
addition  to  the  ther- 
mostatic  control  from 
the  room  to  the  damper, 
as  has  just  been  men- 
tioned, closed  hot  water 
systems  and  steam  and 
vapor  systems  should 
have  regulation  from  the 
pressure  within  the 
boiler  to  the  draft.  Oc- 
casionally in  the  morn- 
ing the  pressure  in 
either  system  may  be- 
come excessive  before 
the  house  is  heated 
enough  for  the  thermo- 
stat to  act.  With  such 


additional   regulation   no   hot   water  heater   or   steam   boiler 
would  te  forced  to  a  dangerous  pressure.     I  ig.  102  shows  a 
thermostat  manufactured  by  the  Andrews  Heating  Co.,  Minne- 
apolis.    The  complete  regulator  has  in  addition 
to  this,  two  cells  of  open  circuit  battery  and  a 
motor  box,  all  of  which  illustrate  very  well  the 
thermostatic  damper  control. 

The  thermostat  operates  by  a  differential 
expansion  of  the  two  different  metals  com- 
posing the  spring  at  the  top.  Any  change  in 
temperature  causes  one  of  the  metals  to  ex- 
pand or  contract  more  rapidly  than  the  other 
and  gives  a  vibrating  movement  to  the  project- 
ing arm.  This  is  connected  with  the  batteries 
and  with  the  motor  in  such  a  way  that  when 
the  pointer  closes  the  contact  with  either  one 
of  the  contact  posts,  a  pair  of  magnets  in  the 
motor  causes  a  crank  arm  to  rotate  through 
180  degrees.  A  flexible  connection  between  this 
crank  and  the  damper  causes  the  damper  to 
open  or  close.  A  change  in  temperature  in 
the  opposite  direction  makes  contact  with  the  other  post 
and  reverses  the  movement  of  the  crank  and  damper.  The 
movement  of  the  arm  between  the  contacts  is  very  small  thus 


TEMPERATURE   CONTROL 


245 


making  the  thermostat  very  sensitive.     No  work  is  required 
of  the   battery  except   that   necessary  to   release   the  motor. 

Occasionally  it  is  desir- 
able to  connect  small  heat- 
ing plants  having  only  one 
thermostat  in  control,  to  a 
central  station  system.  Fig. 
103  shows  how  the  supply 
of  heat  may  be  controlled 
by  the  above  method. 

Fig.  104  shows  the  Syl« 
phon  Damper  Regulator 
made  by  The  American 
Radiator  Co.,  and  applies 
to  steam  pressure  control. 
The  longitudinal  expansion 
of  a  corrugated  brass  or 
copper  cylinder  operates 
the  damper  through  a  sys- 
tem of  levers.  The  longitu- 
dinal movement  of  the  cyl- 
inder is  small  and  hence 
the  bending  of  the  metal 
in  the  walls  of  the  cylinder 
is  very  slight.  This  small 
movement  is  multiplied 


Fig.  104. 


246 


HEATING  AND  VENTILATION 


through  the  system  of  levers  to  the  full  amount  necessary  to 
operate  the  damper.  A  similar  device  is  made  by  the  same 
Company  for  application  to  hot  water  heaters. 

Temperature  control  in  large  plants,  i.  e.,  those  plants  having 
a  large  number  of  heating  units,  is  much  more  complicated. 
In  furnace  systems  this  is  very  much  the  same  as  described 
under  small  plants,  with  additional  dampers  placed  in  the 
air  lines.  The  following  discussions,  therefore,  will  apply 
to  hot  water  and  steam  systems,  and  will  be  additional  to  the 
control  at  the  heater  and  boiler  as  discussed  under  small 
plants.  Fig.  105  shows  a  typical  layout  of  such  a  system. 
Compressed  air  at  15  pounds  per  square  inch  gage  is  main- 
tained in  cylinder,  $«,  which  is  located  in  some  convenient 


Fig.  105. 


place  for  the  attendant.  This  air  is  car- 
ried to  the  thermostat,  T*,  on  one  of  the 
protected  walls  in  the  room.  Here  it 
passes  through  a  controlling  valve  and 
is  then  led  to  the  regulating  valve  on  the 
radiator.  T-his  air  acts  on  the  top  of  a 
rubber  diaphragm  as  shown  in  Fig.  106  to 
close  the  valve  and  to  cut  off  the  sup- 
ply. When  the  room  cools  off,  the  con- 
Fig.  106.  trolling  valve  at  Tn  cuts  off  the  supply 
and  opens  the  air  line  to  the  radiator.  This  removes  the  air 
pressure  above  the  diaphragm  and  permits  the  stem  of  the 


TEMPERATURE  CONTROL  247 

valve  to  lift.     On  the  opening  of  the  valve  the  steam  or  water 
again  enters  the  radiator  and  the  cycle  is  completed. 

Fig-.  66  shows  the  application  of  the  thermostatic  control 
to  the  blower  work.  This  shows  the  thermostat  B  and  the 
mixing  dampers,  located  at  the  plenum  chamber,  in  the 
single  duct  system.  The  same  general  arrangement  could 
be  applied  to  the  double  duct  system,  with  the  dampers  in 
the  wall  at  the  base  of  the  vertical  duct  leading  to  the 
room. 

178.  Some  of  the  Important  Points  in  the  Installation  of 
such  work  are  as  follows.     Each  radiator  has  its  own  regu- 
lating valve.     All   rooms  having  three   radiators   or  less  are 
provided  with  one  thermostat.     Large  rooms  having  four  or 
more  radiators  have  two  or  more  thermostats  with  not  more 
tuan   three   radiators   to   the   thermostat.      Where   other  mo- 
tive power  is   not  available   for  the   air   supply,   a   hydraulic 
compressor   is    used.      This    compressor   automatically    main- 
tains the  air  pressure  at  15  pounds  gage  in  the  steel  supply 
tank.     The  main  air  trunk  lines  are  galvanized  iron,    %   and 
%    inch  in  diameter,  and  are  tested  under  a  pressure   of  25 
pounds  gage.     All  branch  pipes  are  J/4  and  %  inch  galvanized 
iron.  All  fittings  on  the  %  inch  pipes  are  usually  brass.  Where 
flexible    connections    are    made,    this    is    sometimes    done    by 
armoured    lead    piping.      Thermostats    are    usually    provided 
with  metallic  covers,  and  are  finished  to  correspond  with  the 
hardware  of  the  respective  rooms.     Each  thermostat  is  pro- 
vided  with   a   thermometer  and  a   scale   for   making  adjust- 
ments.    Each   radiator  is  provided  with   a  union  diaphragm 
valve  having  a  specially  prepared  rubber  diaphragm  with  felt 
protection.     This  valve  replaces  the  ordinary  radiator  valve. 
One   of  these   valves   is   used   on  the   end   of  each   hot   water 
radiator,     one    on    each    one-pipe    steam    radiator    and    two 
on    each    two-pipe   low   pressure    steam    radiator.      This    last 
condition   does   not   hold   for   two-pipe   steam   radiators   with 
mechanical  vacuum  returns,  in  which  case  patented  special- 
ties are  applied  by  the  vacuum  company.     In  such  cases  the 
supply  to  the  radiator  only  is  controlled.     In  any  first  class 
system  of  control,   the  temperature  of  the   room  may  easily 
be  kept  within  a  maximum  fluctuation  of  three  degrees. 

179.  Some  Special  Designs  of  Apparatus: — All  temperature 
control  work  is  solicited  by  Specialty  Companies,  each  having 
a  patented  system.     In  the   essential  features  these   systems 
all  agree  with  the  foregoing  general  statements.     The  chief 


248 


HEATING  AND  VENTILATION 


difference    is    in    the    principle    upon    which    the    thermostat, 
TK,  operates. 

Pig.  107  shows  a  section  through  the  thermostat  manu- 
factured by  The  Johnson  Service  Co.,  Milwaukee.  The  air 
comes  from  the  supply  tank  through  the  pipe  C  and  enters 


Fig.   107 


the  thermostat  through  the  cut  off  valve  E.  D  leads  to  the 
regulating  valve  at  the  radiator  or  damper.  From  the  valve 
E  the  air  is  led  up  to  F.  F  is  attached  to  the  stem  G  which 
passes  up  through  the  outlet  H  and  carries  the  grooved 
head  I.  If  F  be  moved  up  to  the  inside  opening  of  H,  it 
will  close  the  opening  and  will  open  C  to  D.  It  is  evident, 
since  F  is  against  H,  this  air  cannot  escape  to  the  atmosphere, 
but  passes  to  pipe  D,  thence  to  the  regulating  valve  and 
closes  the  hot  water  or  steam  valve  or  damper.  Should  the 
valve  F  be  again  pushed  to  the  right  hand  seat,  the  supply 
of  compressed  air  will  again  be  closed  off,  the  opening  H  will 
be  uncovered,  the  air  that  has  been  stored  in  the  regulating 
valve  escapes,  and  the  valves  that  have  been  shut  are  thereby 
opened.  From  this  it  will  be  seen  that  as  the  air  valve  F  is 
either  to  the  right  or  left,  the  main  valve  will  be  opened  or 
shut.  The  valve  F  is  moved  by  the  thermostat.  When  valve  F 


TEMPERATURE   CONTROL  249 


is  open  the  lead  seat  N  is  off  the  port  M  and  a  small  amount 
of  air  from  the  line  C  leaks  through.  This  leakage  is  slight 
and  continues  until  N  closes  the  port  again.  The  real  thermo- 
stat is  the  spring  P  Q.  These  are  steel  and  brass  strips 
brazed  together  in  one  piece.  Because  of  a  higher  coefficient 
of  expansion  in  the  one  than  in  the  other,  a  change  in  room 
temperature  causes  N  to  move  toward,  or  away  from,  the 
seat.  As  soon  as  the  temperature  of  the  room  drops  sufficient- 
ly, Q  contracts  more  rapidly  than  P,  and  the  port  closes.  The 
leakage  air  is  then  confined  under  the  diaphragm  K  and  its 
pressure  increases  until  the  lever  W  is  forced  out  and 
valve  F  is  closed.  By  the  closing  of  valve  F,  as  stated  above, 
the  air  is  exhausted  from  above  the  diaphragm  in  the  regu- 
lating valve  and  the  radiator  opens.  The  saddle  R  can  be 
adjusted  so  as  to  make  the  thermostat  more  or  less  sensi- 
tive. To  set  the  thermostat  for  any  desired  temperature 
turn  the  adjusting  post  U  until  the  pointer  Y  indicates  the 
proper  temperature  on  the  diaphragm  ring. 

The  thermostat  as  here  shown  gives  full  movement  to 
the  valve,  i.  e.,  full  open  and  full  closed.  Other  forms  for 
control  are  designed  for  graduated  movement  of  dampers 
where  used  in  blower  systems. 

Fig.  108  shows  a  section  through  the  pattern  K  thermo- 
stat, manufactured  by  the  Powers  Regulator  Co.,  Chicago. 
This  thermostat  consists  of  a  frame  carrying  two  corrugated 
disks,  brazed  together  at  the  circumference  and  containing  a 
volatile  liquid  having  a  boiling  point  at  about  50  degrees  F. 
At  a  temperature  of  about  70  degrees,  the  vapor  within 
the  disks  has  a  pressure  of  about  6  pounds  to  the  square  inch. 
This  pressure  varies  with  every  change  of  temperature  and 
produces  variations  in  the  total  thickness  at  the  center  of 
the  disks. 

The  compressed  air  enters  at  H  and  passes  into  chamber 
N  through  the  controlling  valve  J,  which  is  normally  held  to 
its  seat  by  a  coil  spring  under  cap  P.  Within  the  flange  M 
is  located  an  escape  valve  L  upon  which  the  point  of  the 
supply  valve  J  rests.  Valve  L  tends  to  remain  open  when 
permitted  by  reason  of  the  spring  underneath  the  cap.  When 
the  temperature  rises  sufficiently  to  cause  the  disks  to  in- 
crease in  thickness  and  move  the  flange  M,  the  first  action 
is  to  seat  the  escape  valve  L,  its  spring  being  weaker  than 
that  above  J.  If  the  expansive  motion  is  continued  after 


250 


HEATING  AND  VENTILATION 


valve  L  is  seated,  the  valve  J  is  then  lifted  from  its  seat 
and  compressed  air  flows  into  the  chamber  N.  As  the 
air  accumulates  in  chamber  N,  it  exerts  a  pressure  upon  the 
elastic  diaphragm  K  in  opposition  to  the  expansive  force  of 
the  disk.  So,  whenever  there  is  sufficient  pressure  in  N  to 
balance  the  power  exerted  by  the  disks,  the  valve  J  returns 


Fig.    108. 


to  its  seat  and  no  more  air  is  permitted  to  pass  through. 
If  the  temperature  falls,  the  pressure  within  the  disks  be- 
comes less,  the  disks  draw  together  and  the  over-balancing 
air  pressure  in  N  reverses  the  movement  of  the  flange  M  and 
permits  the  escape  valve  L  under  the  influence  of  its  spring 
to  raise  from  its  seat,  whereupon  a  portion  of  the  air  in  N 
is  discharged  until  the  pressure  in  N  becomes  equal  to  the 
diminished  pressure  from  the  disks.  Thus  the  pressure  of  the 
air  in  N  is  maintained  always  in  direct  proportion  to  the 
expansive  power  (temperature)  of  the  disks.  Port  J  connects 
with  chamber  N  and  leads  to  the  diaphragm  valve. 

This  thermostatic  valve  controls  the- regulator  valve  by 
a    graduated    movement    and    is    used    on    the    dampers    for 


TEMPERATURE   CONTROL, 


251 


blower  work.     Another  form  with  maximum  movement  only 
is  designed  for  steam  systems. 

Fig.  109  shows  sections  through  the  positive  movement 
and  the  graduated  movement  thermostats,  as  manufactured 
by  The  National  Regulator  Co.,  Chicago.  In  the  left  diagram 
air  enters  the  thermostat  through  the  tube  C,  passes  up 
through  the  filter  P  to  the  port  G,  and  from  thence  through 
to  a  similar  tube  D  to  the  regulating  valve  at  the  radiator. 
G  may  be  opened  or  closed  according  as  the  stem  K  controls 


Fig.    109. 

the  lever  O.  The  movement  of  lever  0  is  caused  by  the  ex- 
pansion and  contraction  of  the  vulcanized  rubber  tube  A. 
The  adjusting  screw  J  at  the  top  is  set  to  permit  G  to  open 
and  close  at  any  desired  temperature.  When  the  temperature 
of  the  room  rises  above  the  normal  temperature,  tube  A 
expands,  the  pressure  from  K  is  released,  tube  G  opens  and 
compressed  air  from  the  supply  tank  passes  through  to  the 
regulating  valve  and  shuts  off  the  heat.  Upon  lowering  the 
temperature  in  the  room,  tube  A  contracts,  the  pressure  of 
K  on  block  M  becomes  greater,  the  port  G  closes,  the  con- 
fined air  in  the  tube  D  leading  to  the  regulating  valve  is  ex- 


252  HEATING  AND  VENTILATION 

hausted  to  the  atmosphere,  and  the  heat  is  turned  on.  The 
screw  S  is  set  so  as  to  allow  the  air  to  pass  through  it  in 
very  small  quantities. 

When  a  graduated  movement  is  desired  on  the  regulating 
valve  for  use  in  air  currents,  the  same  thermostat  with 
slight  modifications  is  used.  In  this  case  a  single  pipe  only 
leads  to  the  thermostat.  When  the  tube  A  expands  from  the 
heat  in  the  room,  the  pressure  from  the  rod  K  is  reduced  and 
the  port  G  is  closed.  The  air  is  now  confined  in  the  single 
pipe,  the  pressure  rises  and  the  regulating  valve  is  moved 
in  such  a  position  as  to  cut  off  a  part  or  all  of  the  warm  air 
and  admit  tempered  air.  When  the  temperature  in  the  room 
falls,  because  of  the  admission  of  this  cooler  air,  the  tube  A 
contracts,  and  the  port  O  is  opened  permitting  the  air  to 
escape  and  operate  the  damper  in  the  reverse  direction.  The 
amount  of  air  admitted  to  the  thermostat  is  controlled  by  a 
needle  valve,  hence  its  sensitiveness  can  be  controlled. 


CHAPTER  XV. 

ELECTRICAL,    HEATING. 

In  the  present  state  of  the  heating  business  it  seems 
almost  unnecessary  to  discuss  electrical  heating,  in  any 
serious  way,  in  connection  with  steam  power  plants.  The 
reasons  will  be  seen  in  the  following  brief  discussion. 
Electrical  heating  can  appeal  to  the  public  only  from  the 
standpoint  of  convenience,  since  a  comparison  of  economies 
between  steam,  hot  water  or  warm  air  heating  on  one  hand, 
and  electrical  heating  on  the  other,  is  wholly  against  the 
latter.  Its  application  to  the  processes  of  heating  will  find  its 
greatest  economy  in  connection  with  water  power  plant 
where  the  combustion  of  fuel  is  eliminated  from  the  prop- 
osition. This  discussion  will  not  bear  in  any  way  upon  the 
water  power  generator. 

ISO.    Equations  Employed  in  Electrical  Heating  Design: — 

1  H.  P.  —  746  watts. 

1  H.  P.  =  33000  ft.  Ibs.  per  min.  —  1980000  ft.  Ibs.  per  hr. 

1   B.  t.  u.  =  778  ft.  Ibs. 

1  H.  P.  hr.  =  1980000  -r-  778  =  2545  B.  t.  u.  per  hr. 

1  H.  P.  hr.  =  746  watt  hrs.  =  2545  B.  t.  u.  per  hr. 

1  watt  hr.  =  3.412  B.  t.  u.  per  hr. 

1  watt  hr.  —  3.412  -f-  170  —  .02  sq.  ft.  of  hot  water  rad. 

1  watt  hr.  =  3.412  -^  255  =  .0134  sq.  ft.  of  steam  rad. 

1  kilo-watt  hr.  =  20.1  sq.  ft.  of  hot  water  rad.  (108) 

1  kilo-watt  hr.  =  13.4  sq.  ft.  of  steam  rad.  (109) 

181.  Comparison  between  Electrical  Heating  and  Hot 
Water  and  Steam  Heating: — The  loss  in  transmitting  electric- 
ity from  the  generators  through  the  switchboard  to  the  radi- 
ators may  be  small  or  large,  depending  upon  the  conditions 
of  wiring,  the  current  transmitted  and  the  pressure  on  the 
line.  In  all  probability  it  would  equal  or  exceed  the  trans- 
mission losses  in  hot  water  or  steam  lines.  Assuming  these 
losses  to  be  the  same,  then  a  fair  comparison  may  be  made 
in  the  cost  of  heating  by  the  various  methods.  The  operating 
efficiency  of  an  electric  heater  is  100  per  cent.,  since  all  the 
current  that  is  passed  into  the  heater  is  dissipated  in  the 
form  of  heat  and  no  other  losses  are  experienced.  This  is 


254  HEATING  AND  VENTILATION 

not  true  of  steam  systems  where  the  water  of  condensation 
is  thrown  away  at  fairly  high  temperatures.  Where  elec- 
tricity or  steam  is  generated  and  distributed  all  in  the  same 
building,  there  is  no  line  loss  to  be  accounted  for,  since  all 
of  this  heat  goes  to  heating  the  building  and  counts  as 
additional  radiation. 

Equations  108  and  109  show  the  theoretical  relation 
existing  between  electrical  heating  and  hot  water  and  steam 
heating  compared  at  the  power  plant.  The  following  dis- 
cussion is  based,  therefore,  upon  the  assumption  that  1 
kilo-watt  hour,  in  an  electric  radiator,  will  give  off  the  same 
amount  of  heat  as  20.1  and  13.4  square  feet  of  hot  water  and 
steam  radiation  respectively.  With  coal  having  13000  B.  t.  u. 
per  pound  and  a  furnace  efficiency  of  60  per  cent.,  it  will 
require  3412  -7-  7800  =  .44  pounds  of  coal  per  hour.  If  coal 
co,sts  $2.00  per  ton  of  2000  pounds,  there  will  be  an  actual 
fuel  expense  of  .044  cent.  On  the  other  hand,  assuming  the 
combined  mechanical  efficiency  of  an  engine  or  turbo-gener- 
ator set  to  be  90  per  cent.,  the  heat  from  the  steam  that  is 
turned  into  electrical  energy  per  hour  is  1000  ~  .90  =  1111 
watts,  for  each  kilo-watt  delivered.  Now,  if  this  unit  has 
15  per  cent  thermal  efficiency,  we  have  the  initial  heat  in 
the  steam  equivalent  to  1111  -r-  .15  =  7400  watt  hours.  From 
this  obtain  7400  X  3.412  =  25249  B.  t.  u.  per  hour;  or,  25249 
-^  7800  =  3.2  pounds  of  coal  per  hour.  This,  at  the  same 
rate  as  .shown  above,  would  be  worth  .32  cent.  Comparing, 
the  electrical  generation  actually  costs  7.2  times  as  much  as 
the  other.  This  comparison  has  dealt  with  the  fuel  costs  at 
the  plant  and  has  not  taken  into  account  the  depreciation, 
labor  costs,  etc.,  the  object  being  to  show  relative  efficiencies 
only. 

Another  way  of  looking  at  this  subject  is  as  follows. 
A  fairly  large  turbo-generator  set  (say  500  K.  W.)  will 
deliver  1  kilo-watt  hour  to  the  switchboard  on  20  pounds 
of  steam.  With  10  per  cent,  additional  steam  for  auxiliary 
units,  this  amounts  to  22  pounds  of  steam  per  kilo-watt  hour 
at  the  switchboard.  One  pound  of  steam  generated  in  a 
plant  of  this  kind  with  the  above  efficiencies  and  value  of  coal, 
also  with  a  ,steam  pressure  of  150  pounds  and  a  good  feed 
water  heater,  will  give  to  each  pound  of  steam  approximately 
1000  B.  t.  u.  This  makes  22000  B.  t.  u.  or  2.8  pounds  of  coal 
required  to  each  kilo-watt  output.  This  is  about  10  per  cent, 
less  than  the  above  figures. 


ELECTRICAL  HEATING  255 

The  ratio  of  7  to  1,  as  shown  in  the  above  efficiencies, 
does  not  seem  to  hold  good  in  the  selling  price  to  the  con- 
sumer. In  round  numbers,  district  steam  and  hot  water  heat- 
ing systems  supply  25000  B.  t.  u.  to  the  consumer  for  one 
cent.  The  cost  for  electrical  energy  to  the  consumer  is  be- 
tween 6  and  7  cents  per  kilo-watt.  This  gives  3412  -r-  6.5  — 
525  B.  t.  u.  for  one  cent.  Comparing  with  the  above,  gives 
a  ratio  of  48  to  1. 

182.  The  Probable  Future  of  Electrical  Heating: — Be- 
cause of  the  low  efficiency  of  electrical  heating  as  compared 
to  other  methods  of  heating,  it  is  very  probable  that  it  will 
not  replace  the  other  methods  except  in  so  far  as  the  con- 
veniences of  the  user  is  the  principal  thing  sought  for,  and 
the  expense  of  operating  a  minor  consideration.  In  some 
forms  of  domestic  service,  however,  electrical  heating  is 
sure  to  find  considerable  usefulness.  The  temperatures  of 
low  pressure  steam  and  hot  water*  together  with  the  incon- 
venience of  use,  are  such  as  to  eliminate  them  from  many 
of  the  household  economies.  They  will  probably  continue 
to  be  used  for  house  heating,  water  heating  and  laundry 
work.  Occupations,  however,  that  require  temperatures 
above  250  degrees,  such  as  broiling,  frying,  ironing,  etc.,  the 
electrical  supply  will  be  in  demand. 


REFERENCES. 

References  on  Electrical  Heating. 

TECHNICAL  PERIODICALS. 

The  Heating  and  Ventilating  Magazine.  Electrical  Heating, 
5  eb.  1907,  p.  28.  Electric  Heating,  W.  S.  Hadaway,  Jr.,  Nov. 
1908,  p.  28;  Dec.  1908,  p.  26.  The  Electrical  World,  Vol.  52,  pages 
450,  903,  1112  and  1358,  and  Vol.  53,  pages  5,  274  and  921. 


CHAPTER  XVI. 


SUGGESTIONS  FOR  A  COURSE  OF  INSTRUCTION. 


183.  Preparation  for  the   Course: — In  adapting  this   sub- 
ject to  a  college  course,  it  should,  if  possible,  be  taken  up 
during  the  last  year  of  college  work,  when  the  ^student  can 
have    the    benefit   of   a    large    part   of   the   training   in    Heat, 
Thermodynamics,    Engineering    Design,    and    Steam    Engines 
and    Boilers,    all    of    which    subjects    are    of    great    value    in 
heating   and    ventilating    work.      The    subjects    of   Heat    and 
Thermodynamics    prepare    for    analytical    and    experimental 
investigation    in    heat    transference,    while    a    knowledge    of 
engines,    boilers    and    general    machinery    gives    information 
of  a  more  practical  turn,  the  application  of  which  is  neces- 
sary in  heating  design.     A  course  of  study,  as  outlined  here, 
is    primarily    theoretical    but    it    should    not    stop    there.      To 
be  of  service  in  fitting  a  man  for  active  participation  in  the 
work   after   leaving    school,    it    must    emphasize    such    points 
as   relate   to   the   layout   of   the   drawings   and   to   the   mate- 
rials  used   in   the   construction   as  well.     A   course   fitted  to 
practical   needs   should   not   only   require    a   full   set   of   cal- 
culations for  each  design,  but  it  should  require  a  complete 
layout  of  each  system. 

184.  Administration  of  the  Work: — The  course  should  be 
administered,   part   in  the  class  room,  as   lectures  and   reci- 
tations,  and   part    (a   set   of  designs)    should   be   left   to   the 
student  to  work  up  largely  upon  his  own  responsibility  and 
submit  the  same  for  approval. 

The  work  in  the  class  room  should  be  at  least  two 
hours  per  week,  and  may  be  divided  between  lectures  and 
recitations  in  whatever  manner  is  thought  best.  In  the  lec- 
tures, references  should  be  made  to  the  various  authorities 
on  heating  and  ventilating  with  suggestions  that  these 
authorities  be  looked  up.  The  lectures  should  also  include 
very  full  details  concerning  the  laying  out  of  such  work, 
with  suggestions  concerning  the  proper  selection  of  ma- 
terials. The  recitations  should  be  made  as  practical  as 
possible  to  serve  in  bringing  out  the  points  that  would 
probably  be  confusing  in  developing  the  designs.  All  class 


OUTLINE  OB   A  COURSE  257 

room  work  should  be  timed  to  suit  the  design  under  con- 
sideration, otherwise  the  design  work  and  the  class  room 
work  will  be  independent  rather  than  mutually  helpful. 

185.  Outline  of  the  Work  of  Design: — After  two  or  three 
weeks  devoted  to  the  subjects  of  ventilation,  radiating  sur- 
faces, etc.,  the  work  of  design  should  be  taken  up  and 
might  very  properly  cover  the  following  systems  of  heat- 
ing: 

1.  Furnace  heating,  as  applied  to  residences.     Time  al- 
lowed,  three   weeks. 

2.  Hot  water  heating,   as  applied   to   residences.     Time 
allowed,  three  weeks. 

3.  Steam   heating,   as   applied    to   residences.      Time   al- 
lowed, two   weeks. 

4.  Plenum   system   of  warm  air  heating,    as  applied   to 
schools    and    low    office    buildings.       Time    allowed, 
four  weeks. 

5.  District    heating    from    a    Central    Station.    Time    al- 
lowed, four  weeks. 

The  above  will  be  found  to  cover  the  work  very  thor- 
oughly and  should  be  administered  in  such  a  way  as  to 
remove  as  much  of  the  purely  routine  work  as  ppssible, 
otherwise  the  course  which  is  planned  for  one-half  year's 
work  would  be  too  long  for  the  time  allowed  to  the  aver- 
age student  by  the  school  curriculum.  As  an  illustration, 
the  student  prepared  for  this  work  is  fairly  well  qualified 
to  make  mechanical  drawings,  and  any  relief  which  can  be 
given  from  drawing  work  will  permit  the  equivalent  time 
being  put  to  other  and  more  important  parts  of  the  design. 
This  relief  can  take  the  form  of  prepared  building  plans 
stamped  off  on  standard  sized  paper,  thus  permitting  the 
insertion  of  heating  drawings  on  the  same  pages  without 
the  routine  labor  of  reproducing  an  entirely  new  set  of 
drawings.  These  plans  may  be  made  the  same  size  as  the 
blanks  upon  which  the  calculations  are  submitted,  say,  8% 
x  11  inches  and  should  always  be  different  from  any  pre- 
viously given.  The  final  report  will  then  include  every 
thing  under  one  cover  and  can  be  filed  away  without  dif- 
ficulty. For  sample  set  of  building  plans,  see  Figs.  13,  14 
and  15,  with  the  furnace,  pipes  and  registers  removed. 

186.  Specifications: — It  is  desirable  that  each  man  have 
experience  in  writing  specifications  for  his  own  plans.  This  is 


258  HEATING  AND  VENTILATION 

difficult  for  a  beginner  and  requires  considerable  time  to  d<t 
properly.  It  is  thought  best,  therefore,  to  present  a  brief 
set  of  specifications  (see  Chapter  XVII)  to  show  how  such 
work  is  done  and  let  this  set  be  used  to  g'ive  suggestions 
for  the  more  complete  set.  Originality  in  form  and  sim- 
plicity and  accuracy  of  statement  are  the  principal  points 
to  be  observed.  The  instructor  should  use  his  own  dis- 
cretion in  deciding  how  comprehensive  these  specifications 
shall  be. 

INSTRUCTIONS    FOR    DESIGN    REPORTS. 

Nos.    1,    2    and    3. 
Furnace,    Hot  Water   and   Steam    Systems. 

The  first  three  design  reports  in  heating  and  ventila- 
tion cover  three  lines  of  residence  heating,  i.  e.,  furnact-, 
hot  water  and  steam.  Three  complete  sets  of  plants  of  the 
same  house  are  supplied  to  each  member  of  the  class,  upon 
which  the  heating  designs  may  be  made.  With  these  duplicate 
plans,  the  heat  loss  need  be  calculated  once  only  for  the 
three  designs.  Upon  submitting  report  No.  \,  a  copy  of  the 
heat  loss  should  be  made  to  use  on  Nos.  2  and  3. 

Each  man  shall  submit  designs  which  he  has  himself 
worked  up.  No  objection  will  be  raised  to  two  or  more 
students  working  simultaneously,  checking  each  other's 
figures  and  in  a  general  way  profiting  by  good  suggestions. 
It  is  objectionable,  however,  to  divide  the  work  so  that  each 
man  does  only  a  part.  Designs  that,  in  the  opinion  of  the 
instructor,  have  been  copied,  will  be  rejected  and  marked 
zero. 

Each  design  will  be  submitted  in  a  manilla  cover 
properly  filled  out  with  the  name  of  the  designer,  the  name 
of  the  design  and  the  date.  If  the  design  was  worked  up 
in  conjunction  with  any  other  person  or  persons,  these 
names  should  be  given. 

For  the  convenience  of  the  instructor,  each  report  will 
be  arranged  as  follows: 

1.  Blank  sheet   for  instructor's  corrections. 

2.  Title  page   with   statement   of  the  design. 

3.  Specification  sheets. 

4.  Plans;   basement,  first  floor  and  second  floor. 

5.  Summary  table,  after  the  pattern  of  Table  IX. 

6.  Calculations    and    notes. 


OUTLINE  OP  A  COURSE  259 

The    reports   are   returned   after   correction. 

The  calculations  in  the  furnace  design  will  include,  for 
each  room,  the  heat  loss,  the  cubic  feet  of  air  needed 
each  room  as  a  heat  carrier  (this  should  be  checked  for 
ventilation),  the  heat  loss  (by  formula),  the  cubic  feet  of  air 
needed  per  hour  and  the  areas  of  the  net  registers,  gross 
registers,  stacks  and  leaders;  also,  for  the  entire  plant,  the 
air  supply  ducts  and  the  grate.  Specify  the  type  and  size 
of  the  furnace  installed. 

The  calculations  in  the  hot  water  design  will  include 
the  heat  loss,  the  radiation  in  square  feet  per  room,  the 
radiator  pipe  sizes,  the  riser  pipe  sizes,  the  sizes  of  the 
general  mains  (show  on  plans),  the  gallons  of  water  heat- 
ed per  hour,  the  size  of  the  expansion  tank  (locate  on 
pla'ns)  and  -the  type  and  size  of  the  heater  installed. 

The  calculations  in  the  steam  design  will  include  the 
heat  loss,  the  radiation  in  square  feet  per  room,  the  radiator 
pipe  sizes,  the  riser  pipe  sizes,  the  sizes  of  the  general  mains 
(show  on  plans),  the  pounds  of  steam  condensed  per  hour 
total  and  the  type  and  size  of  the  boiler  installed. 

In  drawing  the  mains  on  the  plans,  it  is  suggested  to 
use  red  ink  for  the  supply  mains  and  black  ink  for  the  re- 
turn mains  'to  avoid  confusion.  It  is  also  suggested  to  use 
arrows  to  denote  the  direction  of  flow  within  the  pipes. 

The  reports  will  be  submitted  as  follows: 

No.  1     19 

No.  2     , 19 

No.   3     19 

INSTRUCTIONS    FOR   DESIGN    REPORT. 

No.   4. 
Plenum  Warm  Air   System. 

These  instructions,  together  with  the  three  building 
plans  (not  shown  here  but  same  as  Figs.  74,  75  and  76 
with  the  heating  plants  removed),  will  form  the  basis  upon 
which  to  design  a  plenum  system  of  warm  air  heating  for 
the  building  shown.  Each  room  is  numbered  and  should 
be  referred  to  in  the  report  by  that  number.  The  heat  loss 
for  each  floor  will  be  estimated  from  some  acceptable 
formula.  If  Carpenter's  formula  is  used,  take 


260  HEATING  AND  VENTILATION 

Basement,    (walls  only  two-thirds  exposed,)    n  =  1. 

First  floor,    (walls   fully  exposed)  n  =  iyz. 

Second  floor,    (same  as  first  floor). 

Corridors,  n  =  2. 

In  the  calculations  the  following  points  should  be 
worked  up  for  each  room:  the  heat  loss,  the  cubic  feet  of 
air  per  hour  as  a  heat  carrier  (this  should  then  be  checked 
for  ventilation),  the  net  area  of  the  register  in  square 
inches,  the  catalog  size  of  the  register  (as  12  x  14  inches) 
and  the  size  of  the  wall  duct  (as  8  x  10  inches).  Bind  also 
the  following:  the  size  of  the  fresh  air  entrance;  the  size 
of  the  main  leader  at  the  plenum  chamber  and  the  sizes 
of  the  principal  branches;  the  square  feet  of  heating  surface; 
the  lineal  feet  of  coils;  the  net  wind  area  at  the  coils;  the 
gross  area  at  the  coils  and  the  arrangement  of  the  coils 
in  sections;  the  horse  power  and  the  revolutions  per  min- 
ute of  the  fan,  including  the  sizes  of  the  inlet  and  the 
outlet  of  the  fan;  and  the  horse  power  of  the  engine  in- 
stalled, including  the  diameter  and  the  length  of  the  stroke. 
In  addition  to  the  above,  select  one  of  the  most  important 
rooms  and  find  the  temperature  of  the  air  at  the  registers 
when  excess  air  is  required  for  ventilation. 

The  principal  work  on  the  plans  will  be  to  lay  out  the 
basement  equipment.  The  engine  and  fan  will  be  placed  in 
room  ....  and  should  contain  all  the  necessary  pieces  of 
apparatus  which  go  to  make  up  the  complete  blower  sys- 
tem. Show  on  the  plans  the  location  of  the  tempering  and 
heating  coils,  how  the  air  is  taken  from  the  outside  of  the 
building,  is  passed  through  the  blower  into  the  plenum 
chamber  and  thence  through  a  system  of  ducts  to  the 
various  parts  of  the  building. 

It  is  understood  that  the  steam  is  to  be  received  at 
the  building  under  a  maximum  gage  pressure  of,  say,  30 
pounds  per  square  inch,  and  is  to  be  used  in  the  coils  under 
a  pressure  of  not  over  5  pounds  gage.  This  reduction  will 
be  accomplished  by  the  use  of  a  pressure  reducing  valve. 
Arrange  the  coils  and  piping  so  either  exhaust  steam  or 
live  steam  may  be  used  in  all  the  coils.  Generally  the  ex- 
haust steam  from  the  fan  engine  is  used  in  the  tempering 
coils  and  live  steam  in  the  main  heating  coils.  After  esti- 
mating the  total  amount  of  heating  surface,  divide  this  into 
tempering  and  heating  coils. 


OUTLINE  OE   A  COURSE  261 

A  back  pressure  valve  should  be  placed  on  the  exhaust 
line  opening  to  the  air  at  the  roof  to  relieve  excessive  back 
pressure  on  the  engine.  Oil  and  steam  separators  should 
also  be  installed. 

It  is  suggested  that  a  separate  plate  be  made  of  the 
heater  room  to  avoid  complications  in  drawing.  This  plate 
should  contain  a  plan  and  elevation  with  all  piping  connec- 
tions and  necessary  valves  clearly  shown. 

Design    No.    4    will    be    submitted 19 

INSTRUCTIONS    FOR   DESIGN    REPORT. 
No.    5. 

Centralized  Hot  Water  or  Steam  System. 

These  instructions  together  with  the  plan  of  the  city, 
Fig.  92,  showing  the  portion  of  the  city  to  be  heated,  will 

form  the  basis  upon  which  to  design  a  centralized 

heating  system  for  the  said  locality.  The  plant  will  be 
installed  in  connection  with  the  municipal  lighting  and 

pumping  stations  located  at and  

streets.  In  reconstructing  the  present  plant  the  building 
•will  not  be  used.  The  equipment,  which  may  be  considered 
as  new,  is  as  follows.  (Italics  indicate  variable  terms.) 

1,  250  K.  W.  direct  current  generator,  direct  driven  from  a 
cross  compound  non  condensing  slow  speed,  Corliss  engine. 

1,  150  K.  W.  direct  current  generator,  direct  driven  from  a 
simple  non  condensing  high  sp^ed  engine. 

1,  7J   K.    W.    alternating   current    generator,    direct   driven 
from  a  simple  non  condensing  high  speed  engine. 

2,  1^    million    gallon,    horizontal   reciprocating    duplex,    city 
water  supply  pumps,  size  14  and  20x12x10  inch. When  the  pump 
is    in    action,    the    pressure    head    against    the    pump    is    60 
pounds  and  the  suction  head  is  10  pounds  per  square  inch. 

The  small  apparatus  in  the  plant  requiring  steam  (boil- 
er feed  pumps,  etc.)  may  be  assumed  at  15  per  cent,  of  the 
total  steam  consumption  of  the  large  units. 

3,  250  H.   P.  water  tube  boilers  are  at  present  supplying 
the  plant  with  steam. 

If  a  hot  water  system  is  used,  pumps  will  be  installed 
to  circulate  the  hot  water  in  the  heating  system.  This 
will  necessitate  an  enlargement  of  the  present  steaming 
boiler  plant.  In  addition  to  this,  extra  boiler  service  may 
be  necessary  to  be  used  as  heaters  or  steamers  for  the  heat- 


262  HEATING  AND  VENTILATION 

ing  system  to  make  up  for  the  deficiency  of  exhaust  steam. 
The  heating  capacity  of  the  system  should  be  limited  to, 
say  125000  square  feet  of  steam  radiation,  or  187500  square 
feet  of  hot  water  radiation. 

Only  that  part  of  the  city  shown  between  the  dotted 
lines  will  be  considered  desirable  heating  territory. 
Allow,  say  9000  square  feet  of  hot  water  radiation  or 
6000  square  feet  of  steam  radiation  to  the  four  sides  of  a 
business  square,  and  about  half  of  this  to  the  four  sides  of  a 
residence  square. 

In  working  up  this  design,  investigate  and  plan  for  the 
following  points:  the  probable  number  of  square  feet  of 
heating  surface  in  the  district;  the  layout  of  the  street 
mains  with  a  section  of  the  conduit;  the  sizes  of  the  mains 
at  the  plant  and  at  several  distant  points  in  the  system, 
the  number  and  sizes  of  the  circulating  pumps;  the  load 
curve  of  the  plant  and  the  amount  of  exhaust  steam  per 
hour  available;  the  size  of  and  the  square  feet  of  heating 
surface  in  the  .exhaust  steam  heaters  for  the  circulating 
system,  if  used;  the  boiler  horse  power  total  and  how  it  is 
divided  into  units;  the  economizer  surface  total  and  how  it 
is  divided  into  units;  the  chimney  diameter  and  height,  and 
the  complete  layout  of  the  plant  including  the  arrangement 
of  the  engines,  boilers,  pumps,  heaters,  pipes,  etc. 

Design  No.    5   will  be   submitted 19... » 


CHAPTER   XVII. 


PLANS    AND    SPECIFICATIONS    FOR    HEATING    SYSTEMS. 


O  wiiei- 
cr 
Purchaser 


187.  In  Planning:  for  and  Executing  Engineering  Con- 
irnctM,  the  responsibilities  assumed  by  the  various  interested 
parties  should  be  thoroughly  studied.  The  following  outline 
shows  the  relationship  between  these  parties  and  the  order  of 
the  responsibility. 

Engineer. 

Superintendent  and  Inspector. 

General  contractor,  Subcontractors,  Foremen  and 
Workmen. 

The  engineer,  the  superintendent  and  the  general  con- 
tractor occupy  positions  of  like  responsibility  with  relation 
to  the  purchaser.  The  first  two  work  for  the  interest  of  the 
purchaser  to  obtain  the  best  possible  results  for  the  least 
money,  and  the  last  endeavors  to  fulfill  the  contract  to  the 
'satisfaction  of  the  superintendent,  at  the  least  possible 
expense  to  himself.  These  view-points  are  quite  different 
and  sometimes  are  antagonistic,  but  both  are  right  and  just. 
Of  the  three  parties,  the  engineer  has  the  greatest  respon- 
sibility. It  is  his  duty  to  draw  up  the  plans  and  to  write 
the  specifications  in  such  a  way,  that  every  point  is  made 
clear  and  that  no  question  of  dispute  may  arise  between  the 
superintendent  and  the  contractor.  His  plans  should  detail 
every  part  of  the  design  with  full  notes.  His  specifications 
should  explain  all  points  that  are  difficult  to  delineate  on  the 
plans.  They  should  give  the  purchaser's  views  covering  all 
preferences,  and  should  definitely  state  where  and  what  ma- 
terials may  be  substituted.  Where  any  point  is  not  definitely 
settled  and  left  to  the  judgement  of  the  contractor,  he  may 
be  expected  to  interpret  this  point  in  his  favor  and  use  the 
cheapest  material  that  in  his  judgment  will  give  good  re- 
sults. This  opinion  may  differ  from  that  held  by  the  pur- 
chaser. All  parts  should  be  made  so  plain  that  no  two  opin- 
ions could  be  had  on  any  important  point.  The  engineer 
should  also  be  careful  that  the  plans  and  specifications  agree 
in  every  part.  The  inspector  is  the  superintendent's  repre- 
sentative on  the  grounds  and  is  supposed  to  inspect  and 


264  HEATING  AND  VENTILATION 

pass  upon  all  materials  delivered  on  the  grounds,  and  the 
quality  of  workmanship  in  installing.  For  such  information 
see  Byrne's  "Inspector's  Pocket-Book".  The  general  con- 
tractor generally  sublets  parts  of  the  contract  to  subcon- 
tractors who  work  through  the  foreman  and  workmen  to 
finish  the  work  upon  the  same  basis  as  the  general  con- 
tractor. 

The  following  brief  set  of  specifications  are  not  con- 
sidered complete  but  are  merely  inserted  to  suggest  how 
such  work  is  done. 

Typical  Specifications. 

TITLE  PAGE: — 

SPECIFICATIONS 

for  the 

MATERIALS  AND  WORKMANSHIP 
Required  to  Install 


(Type  of  system) 
HEATING   AND   VENTILATING   SYSTEM 

in  the 
(Building) 

(Location) 
by 

(Name   of   desig-ner) 

INDEX  PAGE: — 

(To  be  compiled  after  the  specifications  are  written.) 

General   Remarks    to    Contractor. — In    the    following-    specifi- 
cations, all  references  to  the  Owner  or  Purchaser  will  mean 

or    any    person    or    persons    delegated    by 

to  serve  as  the  representative.     The  Super- 
intendent of  Buildings  will  be  the  purchaser's  representative  at 


TYPICAL  SPECIFICATIONS  265 

all  times,  unless  otherwise  definitely  stated.  The  contractor 
will,  therefore,  refer  all  doubtful  questions  or  misunder- 
standings, if  any,  to  the  Superintendent,  whose  decision  will 
be  final.  In  case  of  any  doubt  concerning1  the  meaning  of 
any  part  of  the  plans  or  specifications,  the  contractor  shall 
obtain  definite  interpretation  from  the  superintendent  be- 
fore proceeding  with  the  work. 

These  specifications  with  the  accompanying  plans  and 
details  (Sheets  ....  to  ....  inclusive)  cover  the  purchase  of 
all  the  materials  as  specified  later  (the  same  materials  to 
be  new  in  every  case),  and  the  installation  of  the  same  in  a 
first  class  manner  within  the  above  named  building,  located 
at (street)  (city)  (state). 

It  will  be  understood  that  the  successful  bidder,  herein- 
after called  the  contractor,  shall  work  in  conformity  with 
these  plans  and  specifications  and  shall,  to  the  best  of  his 
ability,  carry  out  their  true  intent  and  meaning.  He  shall 
purchase  and  erect  all  materials  and  apparatus  required  to 
make  the  above  system  complete  in  all  its  parts,  supplying 
only  such  quality  of  materials  and  workmanship  as  will  har- 
monize with  a  first  class  system  and  develop  satisfactory 
results  when  working  under  the  heaviest  service  to  which 
such  plants  are  subjected. 

The  contractor  shall  lay  out  his  own  work  and  be  re- 
sponsible for  its  fitting  to  place.  He  shall  keep  a  competent 
foreman  on  the  grounds  and  shall  properly  protect  his  work 
at  all  times,  making  good  any  damage  that  may  come  to  it, 
or  to  the  building,  or  to  the  work  of  other  contractors  from 
any  source  whatsoever,  which  may  be  chargeable  to  himself 
or  to  his  employees  in  the  course  of  their  operations. 

Any  defects  in  materials  or  workmanship,  other  than 
as  stated  under — (state  exceptions  if  any) — that  may  develop 
within  one  year,  shall  be  made  good  by  the  contractor  upon 
written  notification  from  the  purchaser  without  additional 
cost  to  the  purchaser. 

The  contractor  shall,  wherever  it  is  found  necessary, 
make  all  excavations  and  back-fill  to  the  satisfaction  of  the 
superintendent. 

The  contractor  shall  be  responsible  for  all  cuttings  of 
wood  work,  brick  work  or  cement  work,  found  necessary 
in  fitting  his  materials  to  place,  either  within  or  without  the 
building;  the  cutting  to  be  done  to  the  satisfaction  of  the 
superintendent.  The  contractor  shall  be  required  to  connect 


266  HEATING  AND  VENTILATION 

and  supply  water  and  gas  for  building  purposes,  and  shall 
assume  all  responsibility  for  the  same. 

The  contractor  shall  be  required  to  protect  the  purchaser 
from  damage  suits,  originating  from  personal  injuries  re- 
ceived during  the  progress  of  the  work;  also,  from  actions 
at  law  because  of  the  use  of  patented  articles  furnished  by 
the  contractor;  also,  from  any  lien  or  liens  arising  because 
of  any  materials  or  labor  furnished. 

The  purchaser  reserves  the  right  to  reject  any  or  all 
bids. 

No  changes  in  these  plans  and  specifications  will  be 
allowed  except  upon  written  agreement,  signed  by  both  the 
contractor  and  the  purchaser's  representative. 

System. — Specify  the  system  of  heating  in  a  general  way. 
High  pressure,  low  pressure  or  vacuum.  Direct,  direct- 
indirect  or  indirect  radiation.  Basement  or  attic  mains. 
One  or  two-pipe  connections  to  radiators.  If  ventilation  is 
provided,  state  the  movement  of  the  air  and  the  general 
arrangement  of  fans,  coils  or  other  heating  surfaces.  Single 
or  double  duct  air  lines,  etc. 

Boilers. — 'Specify  type,  number,  size  and  capacity,  steam, 
pressure,  approximate  horse  power,  heating  surface,  grate 
surface  and  kind  of  coal  to  be  used.  Locate  on  plan  and  ele- 
vation. Explain  method  of  setting,  portable  or  brick.  Specify 
also,  flue  connection,  heating  and  water  pipe  connections, 
kind  of  grate,  thermometers,  gages,  automatic  damper  con- 
nection, firing  tools  and  conditions  of  final  tests. 

Conduits  and  Conduit  Mains. — (In  this  it  is  assumed  that  the 
boilers  are  not  within  the  building).  In  addition  to  the  lay- 
out, give  sections  of  the  conduit  on  plans  showing  method 
of  construction,  supporting  and  insulating  pipes,  and  drain- 
age of  pipes  and  conduits.  Specify  quality  and  size  of  mate- 
rials, pitch  and  drainage  of  pipes  and  all  other  points  not 
specially  provided  for  in  the  plans. 

Anchors. — Locate  and  draw  on  plans  and  specify  for  the 
installation  regarding  quality  of  materials. 

Expansion  Joints  or  Take-ups. — Locate  and  draw  on  plans. 
Select  type  of  joint  and  specify  for  amount  of  safe  take-up 
and  for  quality  of  material. 

Mains  and  Returns. — Trace  the  steam  from  the  point  where 
it  enters  the  main,  through  all  the  special  fittings  of  the 

system.  Show  where  the  condensation  is  dripped 

to  the  returns  through  traps  or  separating  devices.  Specify 


TYPICAL  SPECIFICATIONS  267 

amount  and  direction  of  pitch,  kind  of  fittings  (flanged  or 
screwed,  cast  iron  or  malleable  iron),  kind  of  corners  (long 
or  short),  method  of  taking  up  expansion  and  contraction. 
Trace  returns  and  specify  dry  or  wet. 

Branches  to  Risers. — Take  branches  from  top  of  mains  by 
tees,  short  nipples  and  ells,  and  enter  the  bottom  of  the 
risers  by  sufficient  inclination  to  give  good  drainage. 

Risers. — Locate  risers  according  to  plan.  They  shall  be 
straight  and  plumb  and  shall  conform  to  the  sizes  given  on 
the  plans.  No  riser  shall  overlap  the  casing  around  win- 
dows. State  how  branches  are  to  be  taken  off  leading  to 
radiators,  relative  to  the  ceiling  or  floor. 

Radiator  Connections. — Specify,  one-pipe  or  two-pipe,  num- 
ber and  kind  of  valves,  sizes  of  connections  and  hand  or 
automatic  control.  All  connections  shall  allow  for  good 
drainage  and  expansion.  Distinguish  between  wall  radiator 
and  floor  radiator  connections.  If  automatic  control  is  used, 
hand  valves  are  usually  omitted. 

Radiators. — Specify  floor  or  wall  radiators,  with  type, 
height,  number  of  columns  and  number  of  sections.  If  other 
radiators  are  substituted  for  the  ones  that  are  referred  to 
as  acceptable,  they  must  be  of  equal  amount  of  surface  and 
acceptable  to  the  Superintendent.  Specify  brackets  for  wall 
radiators,  also,  air  valves  for  all  radiators,  stating  type 
and  location  on  the  radiator.  Require  all  radiators  to  be 
cleaned  with  water  or  steam  at  the  factory  and  plugged  at 
inlet  and  outlet  for  shipment. 

Piping. — Define  quality,  weight  and  material  in  all  mains, 
branches  and  risers.  All  sizes  above  one  and  one-half  inch 
are  usually  lap  welded.  Piping  should  be  stood  on  end  and 
pounded  to  remove  all  scale  before  going  into  the  system. 
All  pipes  1  inch  and  smaller  should  be  reamed  out  full  size 
after  cutting. 

Fittings. — Specify  quality  of  fittings,  whether  light,  stan- 
dard or  heavy,  malleable  or  cast  iron.  P  ittings  with  imper- 
fect threads  should  be  rejected. 

Valves. — Specify  type  (globe,  gate  or  check),  whether 
flanged  or  screwed,  rough  or  smooth  body,  cast  iron  or 
brass,  and  give  pressure  to  be  carried.  All  valves  should 
be  located  on  the  plans. 

Expansion  Tank. — 'Specify  capacity  of  tank  in  gallons,  kind 
of  tank  (square  or  round,  wood  or  steel),  method  of  connect- 
ing up  with  fittings  and  valves,  and  locate  definitely  on  plan 


268  HEATING  AND  VENTILATION 

and  elevation.  Connect  also  to  fresh  water  supply  and  to 
overflow. 

Hangers  and  Ceiling  Plates. — Wall  radiators  and  horizontal 
runs  of  pipe  shall  be  supported  on  suitable  expansion  hang- 
ers or  wall  supports  that  will  permit  of  absolute  freedom  of 
expansion.  Supports  shall  be  placed  ....  feet  centers.  Pipe 
holes  in  concrete  floors  shall  be  thimbled.  Holes  through 
wooden  walls  and  floors  shall  have  suitable  air  space  around 
the  pipe,  and  all  openings  shall  be  covered  with  ornamental 
floor,  ceiling  or  wall  plates. 

Traps. — Specify  type,  size,  capacity  and  location.  State 
whether  flanged  or  screwed  fittings  are  used  and  whether 
by-pass  connection  will  be  put  in.  Refer  to  plans. 

Pressure  Regulating  Valve. — Specify  type,  size  and  location, 
also,  maximum  and  minimum  steam  pressure,  with  guaran- 
tee to  operate  under  slight  change  of  pressure.  State  if 
by-pass  should  be  used  and  explain  with  plans. 

separators. — Specify  type  (horizontal  or  vertical),  also 
size  and  location. 

Automatic  Control. — The  contractor  will  be  held  responsible 
for  the  installation  of  all  thermostats,  regulator  valves,  air 
compressor,  piping  and  fittings  required  to  equip  all  rooms 
and  halls  with  an  automatic  ....  temperature  control  sys- 
tem. Specify  ^approximate  location  and  number  of  thermo- 
stats with  the  desired  finish.  Specify  in  a  general  way,  reg- 
ulator valves  on  radiators,  quality  of  pipe,  maximum  test 
pressure  for  pipe,  power  for  air  supply  (hydraulic,  pneu- 
matic, etc.),  and  supply  tank.  All  the  materials  in  the  tem- 
perature control  system  shall  be  guaranteed  first  class  by 
the  manufacturer  through  the  contractor,  and  the  system 
shall  be  guaranteed  to  give  perfect  control  for  a  period  of 
(two)  years. 

Fans. — Specify  for  direct  connected  or  belt  driven,  right 
or  left  hand,  capacity,  size,  housing,  direction  of  discharge, 
horse  power,  R.  P.  M.  and  pressure.  State  in  a  general  way 
the  requirements  of  the  fan  wheel,  steel  plate  housing,  shaft, 
bearings  and  the  method  of  lubrication. 

Engine.— Specify  type,  horse  power,  steam  pressure, 
approximate  cut-off,  speed  and  kind  of  control. 

Electric  Motors. — Specify  type,  horse  power,  voltage, 
cycles,  phases  and  R.  P.  M. 

Indirect  Heating  Surface. — Specify  the  kind  of  surface  to 
be  put  in  and  then  state  the  total  number  of  square  feet 


TYPICAL  SPECIFICATIONS  269 

of  surface,  with  the  width,  height  and  depth  of  the  heater. 
State  definitely  how  the  heaters  will  be  assembled,  giving 
free  height  of  heater  above  the  floor.  Describe  damper  con- 
trol, steam  piping  to  and  from  heater,  housing  around  heater, 
connection  from  cold  air  inlet  to  heater  and  connection  from 
heater  to  fan.  See  plans.  The  contractor  will  usually  follow 
installation  instructions  given  by  the  manufacturers  for  the 
erection  of  the  heater  and  engine,  consequently  the  speci- 
fications should  only  bear  heavily  upon  those  points  which 
may  be  varied  to  suit  any  condition.  All  valves,  piping  and 
fittings  in  this  work  should  be  controlled  by  the  general 
specifications  referring  to  these  parts. 

Foundations. — Specify  materials  and  sizes. 

Air  Ducts,  Stacks  and  Galvanized  Iron  Work. — The  drawings 
should  give  the  layout  of  all  the  air  lines,  giving  connections 
between  the  air  lines  and  the  fan  and  the  air  lines  and  the 
registers.  Where  these  air  lines  are  below  the  floor,  the 
conduit  construction  should  be  carefully  noted.  All  gal- 
vanized iron  work  should  be  shown  on  the  plans  and  the 
quality  and  weight  should  be  specified.  Air  lines  should 
have  long  radius  turns  at  the  corners. 

Registers. — Specify  height  above  floor,  nominal  size  of 
register,  method  of  fitting  in  wall,  the  finish  of  the  regis- 
ter and  whether  fitted  with  shutters  or  not. 

Protection  and  Covering. — Specify  kind  and  quality  of  pipe 
covering  and  the  finish  of  the  surface  of  the  covering.  State 
the  amount  of  space  between  heating  pipes  and  unprotected 
woodwork.  Distinguish  between  pipes  that  are  to  be  covered 
and  those  that  are  to  be  painted.  All  radiators  and  piping 
not  covered  should  be  painted  with  two  coats  of  ....  bronze 
or  other  finish  acceptable  to  the  superintendent. 

Completion. — Require  all  rubbish  removed  from  the  build- 
ing and  immediate  grounds  and  deposited  at  a  definite  place. 


APPENDIX 


TABLE    1. 
Squares,    Cubes,    Sq.   Roots,   Cube  Roots,    Circles. 


No. 
Diain. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Oircumf        Area 

.1 

.010 

.001 

.310 

.464 

.314 

.00785 

.2 

.040 

.008 

.447 

.585 

.628 

.03146 

.3 

.090 

.027 

.548 

.669 

,.942 

.07008 

.4 

.160 

.064 

.633 

.737 

1.257 

.12566 

.5 

.250 

.125 

.707 

..794 

1.57CT 

.19635 

.6 

.360 

.216 

.775 

.843 

1.885 

.28274 

.7 

.490 

.343 

.837 

.888 

2.200 

.38485 

.8 

.640 

.512 

.894 

.928 

2.513 

.50260 

.9 

.810 

.729 

.949 

(.965 

2.830 

.63620 

1.0 

1.000 

1.000 

.000 

1.000 

3.1416 

.7854 

1.1 

1.210 

1.331 

.0488 

1.0323 

3.456 

.9503 

1.2 

1.440 

1.730 

.0955 

1.0627 

3.770 

1.1310 

1.3 

1.690 

2.197 

.1402 

1.0914 

4.084 

1.3273 

1.4 

1.960 

2.744 

.1832 

1.1187 

4.398 

1.5394 

1.5 

2.250 

3.375 

1.2247 

1.1447 

4.712 

1.7672 

1.8 

2.560 

4.096 

1.2649 

1.1696 

5.027 

2.0106 

1.7 

2.890 

4.913 

1.3038 

1.1935 

5.341 

2.2698 

1.8 

3.240 

5.832 

1.3416 

1.2164 

5.655 

2.5447 

1.9 

3.610 

6.859 

1.3784 

1.2386 

5.969 

2.8353 

2.0 

4.000 

8.000 

1.4142 

1.2599 

6.283 

3.1416 

2.1 

4.410 

9.261 

1.4491 

1.2806 

6.597 

3.4630 

2.2 

4.840 

10.648 

1.483$ 

1.3006 

6.912 

3.8013 

2.3 

5.290 

12.167 

1.5166 

1.3200 

7.226 

4.1548 

2.4 

5.760 

13.824 

1.5493 

1.3389 

7.540 

4.5239 

2.5 

6.250 

15.625 

1.5811 

1.3572 

7.854 

4.9087 

2.6 

6.760 

17.579 

1.6125 

1.3751 

8.168 

5.3093 

2.7 

7.290 

19.683 

1.6432 

1.3925 

8.482 

5.7250 

2.8 

7.840 

21.952 

1.6733 

1.4095 

8.797 

6.1575 

2.9 

8.410 

24.389 

1.7029 

1.4260 

9.111 

6.6052 

3.0 

9.000 

27.000 

1.7321 

.4422 

9.425 

7.0688 

3.1 

9.610 

29.791 

1.7607 

.4581 

9.739 

7.5477 

3.2 

10.240 

32.768 

1.7889 

.4736 

10.053 

8.0425 

3.3 

10.890 

35.937 

1.8166 

.4888 

10.367 

8.5530 

3.4 

11.560 

39.304 

1.8439 

.5037 

10.681 

9.0792 

3.5 

12.250 

42.875 

1.8708 

1.5183 

10.996 

9.6211 

3.6 

12.960 

46.656 

1.8974 

1.5326 

11.310 

10.179 

3.7 

13.690 

50.653 

1.9235 

1.5467 

11.624 

10.752 

3.8 

14.440 

54.872 

1.9494 

1.5605 

11.938 

11.341 

3.9 

15.210 

59.319 

1.9748 

1.5741 

12.262 

11.946 

4.0 

16.000 

64.000 

2.0000 

1.5870 

12.566 

12.566 

4.1 

16.810 

68.921 

2.0249 

1.6005 

12.881 

13.203 

4.2 

17.640 

74.088 

2.0494 

1.6134 

13.195 

13.854 

4.3 

18.490 

79.507 

2.0736 

1.6261 

13.500 

14.522 

4.4 

19.360 

85.184  ) 

2.0976  . 

1.6380 

13.823 

15.205 

272 


Xo. 

Diam 

Square 

Cube 

Sq. 
Boot 

Cube 
Root 

Circle 

Oircumf 

Area 

4.5 

20.250 

91.125 

2.1213 

1.6510 

14.137 

15.904 

4.6 

21.160 

97.336 

2.1448 

1.6631 

14.451 

16.619 

4.7 

22.090 

103.823 

2.1680 

1.6751 

14.765 

17.349 

4.8 

23.040 

110.592 

2.1909 

1.6869 

15.080 

18.096 

4.9 

24.010 

117.649 

2.2136 

1.6983 

15.394 

18.859 

5.0 

25.000 

125.000 

2.2361 

1.7100 

15.708 

19.635 

5.1 

26.010 

132.651 

2.2583 

1.7213 

16.022 

20.428 

5.2 

27.040 

140.608 

2.2804 

1.7325 

16.336 

21.237 

5.3 

28.090 

148.877 

2.3022 

1.7435 

16.650 

22.062 

5.4 

29.160 

157.464 

2.3238 

1.7544 

16.965 

22.902 

5.5 

30.250 

16S.375 

2.3452 

1.7653 

17.279 

23.758 

5.6 

31.360 

175.616 

2.3664 

1.7760 

17.593 

24.630 

5.7 

32.490 

185.193 

2.3875 

1.7863 

17.907 

25.518 

5.8 

33.640 

195.112 

2.4083 

1.7967 

18.221 

26.421 

5.9 

34.810 

205.379 

2.4290 

1.8070 

18.536 

27.340 

6.0 

36.000 

216.000 

2.4495 

1.8171 

18.850 

28.274 

6.1 

37.210 

226.981 

2.4698 

1.8272 

19.164 

29.225 

6.3 

38.440 

238.328 

2.4900 

1.8371 

19.478 

30.191 

6.3 

39.690 

250.047 

2.5100 

1.8469 

19.792 

31.173 

6.4 

40.960 

262.144 

2.5298 

1.8566 

20.106 

32.170 

6.5 

42.250 

274.625 

2.5495 

1.8663 

20.420 

33.183 

6.6 

43.560 

287.496 

2.5691 

1.8758 

20.735 

34.212 

-       6.7 

44.890 

300.763 

2.5884 

1.8852 

21.049 

35.257 

6.8 

46.240 

314.432 

2.6077 

1.8945 

21.363 

36.317 

6.9 

47.610 

328.509 

2.6268 

1.9088 

21.677 

37.393 

7.0 

49.000 

343.000 

2.6458 

1.9129 

21.931 

38.485 

7.1 

50.410 

357.911 

2.6646 

1.9220 

22.305 

39.592 

7.2 

51.840 

373.248 

2.6833 

1.9310 

22.619 

40.715 

7.3 

53.290 

389.017 

2.7019 

1.9399 

22.934 

41.854 

7.4 

54.760 

405.224 

2.7203 

1.9487 

23.248 

43.008 

7.5 

56.250 

421.875 

2.7386 

1.9574 

23.562 

44.179 

7.6 

57.760 

438.976 

2.7568 

1.9661 

23.876 

45.365 

7.7 

59.290 

456.533 

2.7749 

1.9747 

24.190 

46.566 

7.8 

60.840 

474.552 

2.7929 

1.9832 

24.504 

47.784 

7.9 

62.410 

493.039 

2.8107 

1.9916 

24.819 

49.017 

8.0 

64.000 

512.000 

2.8284 

2.0000 

25.133 

50.266 

8.1 

65.610 

531.441 

2.8461 

2.CC83 

25.447 

51.530 

8.2 

67.240 

551.468 

2.8636 

2.0165 

25.761 

53.810 

8.3 

68.890 

571.787 

2.8810 

2.0247 

26.075 

54.103 

8.4 

70.560 

592.704 

2.8983 

2.0328 

26.389 

55.418 

8.5 

72.250 

614.125 

2.9155 

2.0408 

26.704 

58.745 

8.6 

73.960 

636.056 

2.9326' 

2.0488 

27.018 

58.083 

8.7 

75.690 

658.503 

2.9496 

2.0567 

27.332 

59.447 

8.8 

77.440 

681.473 

2.9665 

2.0646 

27.646 

60.821 

8.9 

79.210 

704.969 

2.9833 

2.0724 

27.960 

62.211 

273 


Circle 

No. 

Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Oircumf 

Area 

9.0 

81.000 

729.000 

3.0000 

2.0801 

28.274 

63.617 

9.1 

82.810 

753.571 

3.0166 

2.0878 

28.588 

65.039 

9.3 

84.640 

778.685 

3.0332 

2.0954 

28.903 

66.476 

9.3 

86.490 

804.357 

3.0496 

2.1029 

29.217 

67.929 

9.4 

88.360 

830.584 

3.0659 

2.1105 

29.531 

69.398 

9.5 

•   90.250 

857.375 

3.0822 

2.1179 

29.845 

70.882 

9.6 

92.160 

884.736 

3.0984 

2.1253 

30.159 

72.383 

9.7 

94.090 

912.673 

3.1145 

2.1327 

30.473 

73.898 

9.8 

96.040 

941.198 

3.1305 

2.1400 

30.788 

75.430 

9.9 

98.010 

970.299 

3.1464 

2.1472 

31.102 

76.977 

10 

100.000 

1000.000 

3.1623 

2.1544 

31.416 

78.540 

11 

121.000 

1331.000 

3.3166 

2.2239 

34.558 

95.033 

12 

144.  COO 

1728.000 

3.4641 

2.2894 

37.699 

113.097 

IS 

169.000 

2197.000 

3.6056 

2.3513 

40.841 

132.732 

14 

196.000 

2744.000 

3.7417 

2.4101 

43.983 

153.938 

15 

225.000 

3375.000 

3.8730 

2.4662 

47.124 

176.715 

16 

256.000 

4096.000 

4.0000 

2.5198 

50.265 

201.062 

17 

289.  000 

4913.000 

4.1231 

2.5713 

53.407 

226.980 

18 

324.000 

5832.000 

4.2426 

2.6207 

56.549 

254.469 

19 

361.000 

6859.000 

4.3589 

2.6684 

59.690 

283.529 

20 

400.000 

8000.000 

4.4721 

2.7144 

62.832 

314.159 

21 

441.000 

9261.000 

4.5826 

2.7589 

65.973 

346.361 

23 

484.000 

10648.000 

4.6904 

2.8021 

69.115 

380.133 

23 

529.000 

12167.000 

4.7958 

2.8439 

72.257 

415.476 

24 

576.000 

13824.000 

4.8990 

2.8845 

75.398 

452.389 

25 

625.000 

15625.000 

5.0000 

2.9241 

78.540 

490.874 

38 

676.000 

17576.000 

5.0990 

2.9625 

81.681 

530.929 

27 

729.000 

19683.000 

5.1962 

3.0000 

84.823 

572.555 

28 

784.000 

21952.000 

5.2915 

3.0366 

87.966 

615.752 

29 

841.000 

24389.000 

5.3852 

3.0723 

91.106 

660.520 

30 

900.000 

27000.000 

5.4772 

3.1072 

94.248 

706.858 

31 

961.000 

29791.000 

5.5678 

3.1414 

97.389 

754.763 

33 

1024.000 

32768.000 

5.6569 

3.1748 

100.531 

804.248 

33 

1089.000 

35937.000 

5.7446 

3.2075 

103.673 

855.299 

34 

1156.000 

39304.000 

5.8310 

3.2396 

106.841 

907.920 

35 

1225.000 

42875.000 

5.9161 

3.2710 

109.956 

962.113 

36 

1296.000 

46656.000 

6.0000 

3.3019 

113.097 

1017.88 

37 

1369.000 

50653.000 

6.0827 

3.3322 

116.239 

1075-31 

38 

1444.000 

54872.000 

6.1644 

3.3620 

119.381 

1134.11 

39 

1521.000 

59319.000 

6.2450 

3.3912 

122.522 

1194.59 

40 

1600.000 

640CO.OOO 

6.3246 

3.4200 

125.66 

1256.64 

41 

1681.000 

68921.0001 

6.4031 

3.4482 

128.81 

1320.25 

42 

1764.000 

74088.  OOO1 

6.4807 

3.4760 

131.95 

1385.44 

43 

1849.000 

79507.000 

6.5574 

3.5084 

135.09 

1452.20 

44 

1936.000 

85184.000 

6.6333 

3.5303 

138.23 

1520.58 

274 


No. 
Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Dircumf 

Area 

45 

2025.000 

91125.000 

6.7082 

3.5569 

141.37 

1590.43 

46 

2116.000 

97336.000 

6.7823 

3.5830 

144.51 

1661.90 

47 

2209.000 

103823.000 

6.8557 

3.6088 

147.65 

1734.94 

48 

2304.000 

110592.000 

6.9282 

3.6342 

150.80 

18C9.56 

49 

2401.000 

117649.000 

7.0000 

3.6593 

153.94 

1885.74 

60 

2500.000 

125000.000 

7.0711 

3.6840 

157.08 

1963-50 

51 

2601.000 

132651.000 

7.1414 

3.7084 

160.22 

2042.82 

53 

2704.000 

140608.000 

7.2111 

3.7325 

163.36 

2123.72 

53 

2809.000 

148877.000 

7.2801 

3.7563 

166.50 

2206.18 

54 

2916.000 

157464.000 

7.3485 

3.7798 

169.65 

2290.22 

55 

3025.000 

166375.000 

7.4162 

3.8030 

172.79 

2375.83 

56 

3136.000 

175616.000 

7.4833 

3.8259 

175.93 

2463.01 

57 

3249.000 

185193.000 

7.5498 

3.8485 

179.07 

2551.76 

58 

S364.000 

195112.000 

7.6158 

3.8709 

182.21 

2642.08 

59 

3481.000 

205379.000 

7.6811 

3.8930 

185.35 

2733.97 

60 

3600.000 

216000.000 

7.7460 

3.9149 

188.50 

2827.43 

61 

3721.000 

226981.000 

7.8102 

3.9365 

191.64 

2922.47 

62 

£844.000 

238328.000 

7.8740 

3.9579 

194.78 

3019.07 

63 

3969.000 

250047.000 

7.9373 

3.9791 

197.92 

3117.25 

64 

4096.000 

262144.000 

8.0000 

4.0000 

201.06 

3216.99 

65 

4225.000 

274625.000 

8.0623 

4.0207 

204.20 

3318.31 

66 

4356.000 

287496.000 

8.1240 

4.0412 

207.34 

3421.19 

67 

4489.000 

300763.000 

8.1854 

4.0615 

210.49 

3525.65 

68 

4624.000 

314432.000 

8.2462 

4.0817 

213.63 

3631.68 

69 

4761.000 

328509.000 

8.3086 

4.1016 

216.77 

3739.28 

70 

4900.000 

343000.000 

8.3666 

4.1213 

219.91 

3848.45 

71 

5041.000 

357911.000 

8.4261 

4.1408 

223.05 

3959.19 

72 

5184.000 

373248.000 

8.4853 

4.1602 

226.19 

4071.50 

73 

5329.000 

389017.000 

8.5440 

4.1793 

229.34 

4185.39 

74 

5476.000 

405224.000 

8.6023 

4.1983 

232.48 

4300.84 

75 

5625.000 

421875.000 

8.6603 

4.2172 

235.62 

4417.86 

76 

5776.000 

438976.000 

8.7178 

4.2358 

238.76 

4536.46 

77 

5929.000 

456533.000 

8.7750 

4.2543 

241.90 

4656.63 

78 

6084.000 

474552.000 

8.8318 

4.2727 

245.04 

4778.36 

79 

6241.000 

493039.000 

8.8882 

4.2908 

248.19 

4901.67 

80 

6400.000 

512000.000 

8.9443 

4.3089 

251.33 

5026.55 

81 

6561.000 

531441.000 

9.0000 

4.3267 

254.47 

5153.00 

82 

6724.000 

551368.000 

9.0554 

4.3445 

257.61 

5281.03 

83 

6889.000 

571787.000 

9.1104 

4.3621 

260.75 

5410.61 

84 

7056.000 

592704.000 

9.1652 

4.3795 

263.89 

5541.77 

85 

7225.000 

614125.000 

9.2195 

4.3968 

267.04 

5674.50 

86 

7396.000 

636056.000 

9.2736 

4.4140 

270.18 

5808.80 

87 

7569.000 

658503.000 

9.3274 

4.4310 

273.32 

6944.68 

88 

7744.000 

681472.000 

9.3808 

4.4480 

276.46 

6082.12 

89 

7921.000 

704969.000 

9.4340 

4.4647 

279.60 

6221.14 

275 


No. 
Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Oircumf        Area 

90 

8100.000 

729000.000 

9.4868 

4.4814 

282.74 

6361.73 

91 

8281.000 

753571.000 

9.5394 

4.4979 

285.88 

6503.88 

92 

8464.000 

778688.000 

9.5917 

4.5144 

289.03 

6647.61 

93 

8649.000 

804357.000 

9.6437 

4.5307 

292.17 

6792.91 

94 

8836.000 

830584.000 

9.6954 

4.5468 

295.31 

6939.78 

95 

9025.000 

857375.000 

9.7468 

4.5629 

298.45 

7088.22 

99 

9216.000 

884736.000 

9.7980 

4.5789 

301.59 

7238.23 

97 

9409.000 

912673.000 

9.8489 

4.5947 

30i.73 

-     7389.81 

98 

9604.000 

941192.000 

9.8995 

4.6104 

307.88 

7542.96 

99 

9801.000 

970299.000 

9.9499 

4.6261 

311.02 

7697.69 

100 

10000.000 

1000000.  000 

10.0000 

4.6416 

314.16 

7853.98 

105 

11025.000 

1157625.000 

10.2470 

4.7177 

329.87 

8659.01 

110 

12100.000 

1331000.000 

10.4881 

4.7914 

345.58 

9503.32 

115 

13225.000 

1520875.000 

10.7238 

4.8629 

361.28 

10388.89 

120 

14400.000 

1728COO.OOO 

10.9545 

4.9324 

376.99 

11309.73 

125 

15625.000 

1953125.000 

11.1803 

5.0000 

392.70 

12271.85 

130 

16900.000 

2197000.000 

11.4018 

5.0658 

408.41 

13273.23 

135 

18225.000 

2460375.000 

11.6190 

5.1299 

424.12 

14313.88 

140 

19600.000 

2744000.000 

11.8322 

5.1925 

439.82 

15393.80 

145> 

2102-5.000 

3048625.000 

12.0416 

5.2536 

455.53 

16513.00 

150 

22500.000 

3375000.000 

12.2474 

5.3133 

471.24 

17671.46 

155 

24025.000 

3723875.000 

12.4499 

5.3717 

486.95 

18869.19 

160 

25600.000 

4096000.000 

12.6491 

5.4288 

502.65 

20106.19 

165 

27225.000 

4493125.000 

12.8452 

5.4848 

518.36 

21382.46 

170 

28900.000 

4913000.000 

13.0384 

5.5397 

534.07 

22698.01 

175 

30625.000 

£359375.000 

13.2288 

5.5934 

549.78 

24052.82 

180 

32400.000 

5832000.000 

13.4164 

5.6462 

565.49 

25446.90 

185 

3-1225.000 

6331625.000 

13.6015 

5.6980 

581.19 

26880.25 

190 

36100.000 

6859000.000 

13.7840 

5.7489 

596.90 

28352.87 

195 

38025.000 

7414875.000 

13.9642 

5.7989 

612.61 

29864.77 

200 

40000.000 

8000000.000 

14.1421 

5.8480 

628.32 

31415.93 

205 

42025.000 

8615125.000 

14.3178 

5.8964 

644.03 

33006.36 

210 

44100.000 

9261000.000 

14.4914 

5.9439 

659.73 

34636.06 

215 

46225.000 

9938375.000 

14.6629 

5.9907 

675.44 

36305.03 

230 

48400.000 

10648000.000 

14.8324 

6.0368 

691.15 

38013.27 

225 

50625.000 

11390625.000 

15.0000 

6.0822 

706.86 

39760.78 

230 

52900.000 

12167000.000 

15.1658 

6.1269 

722.57 

41547.56 

235 

55225.000 

12977875.000 

15.3297 

6.1710 

738.27 

43373.61 

240 

57600.000 

13824000.000 

15.4919 

6.2145 

753.98 

45238.93 

245 

60025.000 

14706125.000 

15.6525 

6.2573 

769.69 

47143.52 

350 

62500.000 

15625000.000 

15.8114 

6.2996 

785.40 

49087.39 

255 

65025.000 

16581375.000 

15.9687 

6.3413 

801.11 

51070.52 

260 

67600.000 

17576000.000 

16.1245 

6.3825 

816.81 

53092.92 

265 

70225.000 

18609625.000 

16.2788 

6.4232 

832.52 

55154.59 

270 

72900.000 

19683000.000 

16.4317 

6.4633 

848.23 

67255.63 

276 


No, 
Diam. 

Square 

Cube 

Sq. 
Boot 

Cube 
Root 

Circle 

Oircumf 

Area 

275 

75625.000 

20796875.000 

16.5831 

6.5030 

863.94 

59395.74 

280 

78400.000 

21952000.000 

16.7332 

6.5421 

879.65 

01575.28 

285 

81225.000 

23149125.000 

16.8819 

6.5808 

895.35 

63793.97 

290 

84100.000 

24389000.000 

17.0294 

6.6191 

911.00 

66051.99 

295 

87025.000 

25672375.000 

17.1756 

0.6569 

926.77 

08349.28 

800 

90000.000 

27000000.000 

17.3205 

6.6943 

942.48 

70085.83 

305 

93025.000 

28372625.000 

17.4642 

6.7313 

958.19 

73061.66 

310 

96100.000 

29791000.000 

17.6068 

6.7679 

973.89 

75476.76 

315 

99225.000 

31255875.000 

17.74821 

6.8041 

989.60 

77931.13 

320 

102400.000 

32768000.000 

17.8885 

6.8399 

1005.31 

80424.77 

325 

105625.000 

34328125.000 

18.0278 

6.8753 

1021.021 

82957.68 

330 

108900.000 

35937000.000 

18.1659 

6.9104 

1036.73 

85529.86 

335 

112225.000 

37595375.000 

18.3030 

6.9451 

1052.43 

88141.31 

340 

115600.000 

39304000.000 

18.4391 

6.9795 

1068.14 

90792.03 

345 

119025.000 

41063625.000 

18.5742 

7.0130 

1083.85 

93482.00 

350 

122500.000 

42875000.000 

18.7063 

7.0473 

1099.50 

96211.28 

355 

126025.000 

44738875.000 

18.8414 

7.0807 

1115.27 

98979.80 

360 

129600.000 

46656000.000 

18.9737 

7.1138 

1130.97 

101787.60 

365 

133225.000 

48627125.000 

19.1050 

7.1460 

1140.68 

104034.67 

370 

136900.000 

50653000.000 

19.2354 

7.1791 

1162.39 

107521.01 

375 

140625.000 

52734375.000 

19.3649 

7.2112 

1178.10 

110440.62 

380 

144400.000 

54872000.000 

19.4936 

7.2432 

1193.81 

113411.49 

385 

148225.000 

57066625.000 

19.6214 

7.2748 

1209.51 

116415.64 

390 

152100.000 

59319000.000 

19.7484 

7.3061 

1225.22 

119459.06 

395 

156025.000 

61629875.000 

19.8746 

7.3372 

1240.93 

122541.75 

400 

160000.000 

64000000.000 

20.0000 

7.3681 

1256.64 

125663.71 

405 

164025.000 

66430125.000 

20.1246 

7.3980 

1272.35 

123824.93 

410 

168100.000 

68921000.000 

20.2485 

7.4290 

1288.05 

132025.43 

415 

172225.000 

71473375.000 

20.3715 

7.4590 

1303.76 

135205.20 

420 

176400.000 

74088000.000 

20.4939 

7.4889 

1319.47 

138544.24 

425 

180625.000 

76765625.000 

20.6155 

7.5185 

1335.18 

141802.54 

430 

184900.000 

79507000.000 

20.7364 

7.5478 

1350.88 

145220.12 

435 

189225.000 

82312875.000 

20.8567 

7.5770 

1306.59 

148616.97 

440 

193600.000 

85184000.000 

20.9762 

7.6059 

1382.30 

152053.08 

445 

198025.000 

88121125.000 

21.0950 

7.6346 

1398.01 

155528.47 

450 

202500.000 

91125000.000 

21.2132 

7.6631 

1413.72 

159043.13 

455 

207025.000 

94196375.000 

21.3307 

7.6914 

1429.42 

162597.05 

460 

211600.000 

97336000.000 

21.4476 

7.7194 

1445.13 

106190.25 

465 

216225.000 

100544625.000 

21.5639 

7.7473 

1400.84 

169822.72 

470 

220900.000 

103823000.000 

21.6795 

7.7750 

1476.55 

173494.45 

475 

225625.000 

107171875.000 

21.7945 

7.o025 

1492.20 

177205.46 

480 

230400.000 

110592000.000 

21.9089 

7.8297 

1507.90 

180955.74 

485 

235225.000 

114084125.000 

22.0227 

7.8508 

1523.67 

184745.28 

490 

240100.000 

117649000.000 

22.1359 

7.8837 

1539.38 

183574.10 

495 

245025.000 

121287375.000 

22.2486 

7.9105 

1555.09 

192442.18 

500 

250000.000 

125000000.000 

22.3607 

7.9370 

1570.80 

196349.54 

277 


TABLE  2. 
Properties   of   Saturated   Steam.* 


Absolute 
press  're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  F. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32° 

1 

101.84 

69.8 

1034.7 

1104.5 

3 

126.15 

94.2 

1021.9 

1116.1 

3 

141.52 

109.6 

1012.2 

1121.8 

4 

153.00 

121.0 

1005.5 

1126.5 

5 

162.26 

130.3 

1000.0 

1130.3 

G 

170.07 

138.1 

995.5 

1133.6 

7 

176.84 

144.9 

991.4 

-    1136.3 

8 

182.86 

150.9 

987.8 

1138.7 

9 

188.27 

156.4 

984.5 

1140.9 

10 

193.21 

161.3 

981.4 

1142.7 

11 

197.74 

165.9 

978.6 

1144.6 

12 

201.95 

170.1 

976.0 

1146.1 

13 

205.87 

174.1 

973.6 

1147.7 

14 

209.55 

177.8 

971.2 

1149.0 

14.7 

212.00 

180.3 

969.7 

1150.0 

15 

213.03 

181.3 

969.1 

1150.4 

16 

216.31 

184.6 

967.0 

1151.6 

17 

219.43 

187.8 

965.0 

1152.8 

18 

222.40 

190.8 

963.1 

1153.9 

19 

225.24 

193.7 

981.2 

1154.9 

20 

227.95 

196.4 

059.4 

1155.8 

21 

230.56 

199.1 

957.7 

1156.8 

22 

233.07 

201.6 

956.0 

1157.6 

23 

235.50 

204.1 

954.4 

1158.5 

84 

237.82 

206.4 

952.9 

1159.3 

25 

240.07 

208.7 

951.4 

1160.1 

26 

242.26 

210.9 

949.9 

1160.8 

27 

244.36 

213.0 

948.5 

1161.5 

28 

246.41 

215.1 

947.1 

1162.2 

29 

248.41 

217.2 

945.8 

1163.0 

60 

250.34 

219.1 

944.4 

1163.5 

81 

252.22 

221.0 

943.1 

1164.1 

82 

254.05 

222.9 

941.8 

1164.7 

S3 

255.84 

224.7 

940.6 

1165.3 

84 

257.59 

226.5 

939.4 

1165.9 

35 

259.29 

228.2 

938.3 

1166.4 

86 

260.96 

229.9 

937.1 

1167.0 

87 

262.  5K 

231.6' 

935.9 

1167.5 

38 

264.17 

233.2 

934.8 

1168.0 

89 

265.73 

234.8 

933.7 

1168.6 

40 

267.20 

236.4 

932.6 

1169.0 

41 

268.76 

237.9 

931.6 

1169.6 

42 

270.23 

239.4 

930.6 

1170.0 

43 

271.66 

240.8 

929.5 

1170.3 

44 

273.07 

242.3 

928.5 

1170.8 

'Condensed  from  Peabody's  Steam  Tables. 
278 


Absolute 
press're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  F. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32° 

45 

274.46 

243.7 

927.5 

1171.2 

46 

275.83 

245.1 

926.6 

1171.7 

47 

277.16                    246.4 

925.6                    1172.0 

48 

278.47 

247.8 

924.7 

1172.5 

49 

279.76 

249.1 

923.8 

1172.9 

50 

281.03 

250.4 

922.8 

1173.2 

51 

282.28 

251.7 

921.9 

1173.6 

52 

283.52 

253.0 

921.0 

1174.0 

53 

284.74 

254.2 

920.1 

1174.3 

54 

285.93 

255.4 

919.3 

1174.7 

55 

287.09 

256.6 

918.4 

1175.0 

66 

288.25 

257.8 

917.6 

1175.4 

57 

289.40 

259.0 

916.7 

1175.7 

58 

290.53 

260.1 

915.9 

1176.0 

59 

291.64 

261.3 

915.1 

1176.4 

60 

292.74 

262.4 

914.3 

1176.7 

61 

293.82 

263.5 

913.5 

1177.0 

62 

294.88 

264.6 

912.7 

1177.3 

63 

295.93 

265.7 

911.9 

1177.6 

64 

296.97 

266.7 

911.1 

1177.8 

65 

298.00 

267.8 

910.4 

1178.3 

66 

299.02 

268.8 

909.6 

1178.4 

67 

300.02 

269.8 

908.9 

1178.7 

68 

301.01 

270.9 

908.1 

1179.0 

69 

301.99 

271.9 

907.4 

1179.3 

70 

302.96 

272.9 

906.6 

1179.5 

71 

S03.91 

273.8 

905.9 

1179.7 

72 

304.86 

274.8 

905.3 

1180.0 

73 

305.79 

275.8 

904.5 

1180.3 

74 

306.72 

270.7 

903.8 

1180.5 

75 

307.64 

277.7 

903.1 

1180.8 

76 

308.54 

278.6 

902.4 

1181.0 

77 

309.44 

279.5 

901.8 

1181.3 

78 

310.33 

280.4 

901.1 

1181.5 

79 

311.21 

281.3 

900.4 

1181.7 

80 

312.08 

282.2 

899.8 

1182.0 

81 

312.94 

283.1 

899.1 

1182.2 

82 

313.79 

283.9 

898.5 

1182.4 

83 

314.63 

284.8 

897.8 

1182.6 

84 

315.47 

285.7 

897.2 

1182.9 

85 

316.30 

286.5 

896.6 

1183.1 

86 

317.12 

287.4 

895.9 

1183.3 

87 

317.93 

288.2 

895.3 

1183.5 

88 

318.73 

289.0 

894.7 

1183.7 

89 

319.53 

289.9 

894.1 

1184.0 

90 

320.32 

290.7 

893.5 

1184.2 

91 

321.10 

291.5 

892.9 

1184.4 

92 

321.88 

292.3 

892.3 

1184.6 

93 

322.65 

293.1 

891.7 

1184.8 

94 

323.41 

293.9 

891.1 

1185.0 

279 


Absolute 
press  're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  P. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32° 

95 

324.16 

294.6 

890.5 

1185.1 

96 

324.91 

295.4 

889.9 

1185.3 

97 

325.66 

296.2 

889.3 

1185.5 

98 

326.40 

296.9 

888.7 

1185.6 

99 

327.13 

297.7 

888.2 

1185.9 

100 

327.86 

298.5 

887.6 

1186.1 

101 

328.58 

299.2 

887.0 

1186.2 

102 

329.30 

299.9                     886.5 

1186.4 

103 

330.01 

300.6                     885.9 

1186.5 

104 

330.72 

301.4 

885.3 

1186.7 

105 

331.42 

302.1 

884.8 

1186.9 

106 

332.11 

302.8 

884.3 

1187.1 

107 

332.79 

303.5 

883.7 

1187.2 

108 

333.48 

304.2 

883.2 

1187.4 

109 

334.16 

304.9 

882.6 

1187.5 

110 

334.83 

305.6 

882.1 

1187.7 

111 

335.50 

306.3 

881.6 

1187.9 

112 

336.17 

307.0 

881.0 

1188.0 

113 

336.83 

307.7 

880.5 

1188.2 

114 

337.48 

308.3 

880.0 

1188.3 

115 

338.14 

309.0 

879.5 

1188.5 

116 

338.78 

309.7 

879.0 

1188.7 

117 

339.42 

310.3 

878.5 

1188.8 

118 

340.06 

311.0                      878.0 

1189.0 

119 

340.69 

311.7 

877.4 

1189.1 

120 

341.31 

312.3 

876.9 

1189.2 

121 

341.94 

312.9 

876.4 

1189.3 

123 

342.56 

313.6 

875.9 

1189.5 

123 

343.18 

314.2 

875.4 

1189.6 

124 

343.79 

314.8 

875.0 

1189.8 

125 

344.39 

315.5 

874.5 

1190.0 

126 

345.00 

316.1 

874.0 

1190.1 

127 

345.60 

316.7 

873.5 

1190.2 

128 

346.20 

317.3 

873.0 

1190.3 

129 

346.79 

317.9 

872.6 

1190.5 

130 

347.38 

318.6 

872.1 

1190.7 

131 

347.96 

319.2 

871.6 

1190.8 

132 

348.55 

319.8 

871.1 

1190.9 

133 

349.13 

320.4 

870.7 

1191.1 

134 

349.70 

320.9 

870.2 

1191.1 

135 

350.27 

321.5 

869.8 

1191.3 

136 

350.84 

322.1 

869.3 

1191.4 

137 

351.41 

322.7 

868.8 

1191.6 

138 

351.98 

323.3 

868.3 

1191.6 

139 

352.54 

323.9 

867.9 

1191.8 

140 

353.09 

324.4 

867.4 

1191.8 

141 

353.65 

325.0 

867.0 

1192.0 

142 

354.20 

325.6 

866.5 

1192.1 

143 

354.75 

326.2 

866.1 

1192.3 

144 

355.29 

326.7 

865.6 

1192.3 

280 


Absolute 
press  're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  F. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32® 

1 

145 

355.83 

327.3 

865.2 

1193.5 

140 

356.37 

337.8 

864.8 

1192.6 

147 

356.91 

328.4 

864.3 

1192.7 

148 

357.44 

328.9 

863.9 

1192.8 

149 

357.97 

329.5 

863.5 

1193.0 

150 

358.50 

330.0 

863.0 

1193.0 

151 

359.03 

330.6 

863.6 

1193.2 

153 

359.54 

331.1 

862.2 

1193.3 

153 

360.06 

331.6 

861.8 

1193.4 

154 

360.57 

332.2 

861.3 

1193.5 

155 

361.09 

332.7 

860.9 

1193.6 

156 

361.60 

333.2 

860.5 

1193.7 

157 

363.11 

333.8 

860.1 

1193.9 

158 

363.62 

334.3 

859.6 

1193.9 

159 

363.13 

334.8 

859.3 

1194.0 

160 

363.63 

335.3 

858.8 

1194.1 

161 

364.12 

335.9 

858.4 

1194.3 

162 

364.62 

336.4 

858.0 

1194.4 

163 

365.11 

336.9 

857.6 

1194.5 

164 

365.60 

337.4 

857.2 

1194.6 

165 

366.09 

337.9 

856.8 

1194.7 

166 

366.58 

338.4 

856.4 

1194.8 

167 

367.06 

338.9 

856.0 

1194.9 

168 

367.54 

339.4 

855.6 

1195.0 

169 

368.03 

339.9 

855.3 

1195.1 

170 

368.50 

340.4 

854.8 

1196.2 

171 

368.97 

340.9 

854.4 

1195.3 

173 

369.45 

341.4 

854.0 

1195.4 

173 

369.93 

341.8 

853.6 

1195.4 

174 

370.39 

342.3 

853.3 

1195.5 

175 

370.86 

342.8 

852.8 

1195.6 

176 

371.33 

343.3 

852.4 

1195.7 

177 

371.78 

343.8 

853.0 

1195.8 

178 

373.24 

344.2 

851.6 

1195.8 

179 

373.70 

344.7 

851.3 

1196.0 

180 

373.16 

345.2 

850.9 

1196.1 

181 

373.61 

345.7 

850.5 

1196.2 

183 

374.07 

346.2 

850.1 

1196.3 

183 

374.53 

346.6 

849.7 

1196.3 

184 

374.98 

347.1 

849.4 

1196.5 

185 

375.41 

347.5 

849.0 

1196.5 

186 

375.86 

348.0 

848.6 

1196.6 

187 

376.30 

348.5 

848.3 

1196.7 

188 

376.74 

348.9 

847.8 

1198.7 

189 

377.18 

349.4 

847.5 

1196.9 

190 

377.61 

349.8 

847.1 

1196.9 

191 

378.05 

350.3 

846.8 

1197.1 

192 

378.49 

350.7 

846.4 

1197.1 

193 

378.92 

351.3 

846.0 

1197.2 

194 

379.35 

351.6 

845.7 

1197.3 

281 


Absolute 
press're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  F. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32° 

195 

379.78 

352.1 

845.3 

1197.4 

196 

380.20 

352.5 

844.9 

1197.4 

197 

380.63 

353.0 

844.6 

1197.6 

198                      381.05 

353.4 

844.2 

1197.6 

19£ 

381.47 

353.8 

843.9 

1197.7 

200 

381.89 

354.3 

843.5 

1197.8 

201 

382.31 

354.  '< 

843.1 

1197.8 

202 

S82.73 

355.1 

842.8 

1197.9 

203 

383.15 

355.6 

842.4 

1198.0 

204 

383.56 

356.0 

842.1 

1198.1 

5-05 

383.98 

356.4 

841.7 

1198.1 

£06 

384.39 

356.9 

841.3 

1198.2 

2O7 

384.80 

357.3 

841.0 

1198.3 

208 

385.21 

357.7 

840.7 

1198.4 

209 

385.61 

358.1 

840.3 

1198.4 

310 

386.02 

358.6 

840.0 

1198.6 

211 

386.42 

359.0 

839.6 

1198.6 

212 

386.82 

359.4 

839.3 

1198.7 

213 

387.22 

359.8 

839.0 

1198.8 

214 

387.62 

360.2 

838.6 

1198.8 

215 

388.02 

360.6 

838.3 

1198.9 

216 

388.41 

361.0 

837.9 

1198.9 

217 

388.80 

361.4 

837.6 

1199.0 

218 

389.20 

361.9 

837.2 

1199.1 

219 

389.59 

362.3 

836.9 

1199.2 

230 

389.98 

362.7 

836.6 

1199.3 

221 

390.37 

363.1 

836.2 

1199.3 

222 

390.76 

363.5 

835.9 

1199.4 

223 

391.14 

363.9 

835.6 

1199.5 

224 

391.53 

364.3 

835.2 

1199.5 

225 

391.91 

364.7 

834.9 

1199.8 

226 

392.29 

365.1 

834.6 

1199.7 

227 

392.67 

365.5 

834.3 

1199.8 

228 

393.04 

365.9 

833.9 

1199.8 

229 

393.42 

366.2 

833.6 

1199.8 

230 

393.80 

366.6 

833.3 

1199.9 

231 

394.18 

367.0 

832.9 

1199.9 

232 

394.56 

367.4 

832.6 

1200.0 

233 

394.93 

367.8 

832.3 

1200.1 

234 

395.30 

368.2 

832.0 

1200.2 

235 

395.67 

368.6 

831.7 

1200.3 

236 

396.04 

369.0 

831.3 

1200.3 

237 

396.41 

369.4 

831.0 

1200.4 

238 

c96.78 

369.7 

830.7 

1200.4 

239 

397.14 

370.1 

830.4 

1200.5 

240 

397.50 

370.5 

830.1 

1200.6 

241 

397.86 

370.9 

829.8 

1200.7 

242 

398.22 

371.2 

829.5 

1200.7 

243 

398.59 

371.6 

829.1 

1200.7 

244 

398.96 

372.0 

828.8 

1200.8 

282 


Absolute 
press're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
Degrees  F. 

Heat 
of  the 
Liquid 

Heat  of  the 
Vaporiza- 
tion 

Total 
Heat 
Above  32° 

245 

399.32 

372.4 

828.5 

1200.9 

246 

399.68 

372.8 

828.2 

1201.0 

247 

400.04 

373.2 

827.8 

1201.0 

248 

400.39 

373.5 

827.5 

1201.0 

249 

400.75 

373.9 

827.2 

1201.1 

250 

401.10 

374.2 

826.9 

1201.1 

251 

401.45 

374.6 

826.6 

1201.2 

262 

401.79 

375.0 

826.3 

1201.3 

253 

402.14 

375.3 

826.0 

1201.3 

254 

402.48 

375.7 

825.7 

1201.4 

255 

402.83 

376.0 

825.4 

1201.4 

256 

403.17 

376.4 

825.1 

1201.6 

257 

403.52 

376.8 

824.8 

1201.6 

258 

403.86 

377.1 

824.5 

1201.6 

259 

404.21 

377.5 

824.2 

1201.7 

260 

404.55 

377.8 

823.9 

1201.7 

261 

404.89 

378.2 

823.6 

1201.8 

262 

405.23 

378.5 

823.3 

1201.8 

263 

405.57 

378.9 

823.0 

1201.9 

264 

405.90 

379.2 

822.7 

1201.9 

265 

406.23 

379.6 

822.4 

1202.0 

268 

406.57 

379.9 

822.1 

1202.0 

267 

406.90 

380.3 

821.8 

1202.1 

268 

407.23 

380.6 

821.5 

1202.1 

.       269 

407.57 

381.0 

821.2 

1202.2 

270 

407.90 

381.3 

820.9 

1202.2 

•     271 

408.23 

381.7 

820.6 

1202.3 

272 

408.57 

382.0 

820.3 

1202.3 

273 

408.90 

382.4 

820.1 

1202.5 

274 

409.23 

382.7 

819.8 

1202.5 

275 

409.57 

383.1 

819.5 

1202.6 

276 

409.90 

383.4 

819.2 

1202.6 

277 

410.23 

383.8 

818.9 

1202.7 

278 

410.55 

384.1 

818.6 

1202.7 

279 

410.87 

384.4 

818.3 

1202.7 

280 

411.19 

384.8 

818.0 

1202.8 

281 

411.52 

385.1 

817.7 

1202.8 

411.84 

385.4 

817.4 

1202.8 

283 

412.16 

385.8 

817.2 

1203.0 

284 

412.47 

386.1 

816.9 

1203.0 

285 

412.78 

386.4 

816.6 

1203.0 

286 

413.09 

386.7 

816.3 

1203.0 

287 

413.41 

387.1 

8i6.0 

1203.1 

288 

413.72 

387.4 

815.8 

1203.2 

289 

414.03 

387.7 

815.5 

1203.2 

290 

414.35 

388.1 

815.2 

1203.3 

291 

414.68 

388.4 

814.9 

1203.3 

293 

415.00 

388.7 

814.0 

1203.3 

293 

415.31 

389.1 

814.3 

1203.4- 

294 

415.63 

389.4 

814.1 

1203.5 

283 


Absolute 
Pressure 
Pounds  Per 
Square  Inch 

Temperature 
Degrees 
Fahrenheit 

Heat  of  the 
Liquid 

Heat  of  the 
Vaporization 

Total  Heat 
Above  32 

295 

415.95 

389.7 

813.8 

1203.5 

293 

416.24 

390.0 

813.5 

1203.5 

297 

416.55 

390.4 

813.2 

1203.6 

298 

416.85 

390.7 

813.0 

1203.7 

299 

417.15 

391.0 

812.7 

1203.7 

300 

417.45 

391.3 

812.4 

1203.7 

301 

417.76 

391.6 

812.1 

1203.7 

303 

418.06 

391.9 

811.9 

1203.8 

303 

418.36 

392.3 

811.6 

1203.9 

804 

418.67 

392.6 

811.3 

1203.9 

SOS 

418.97 

392.9 

811.1 

1204.0 

306 

419.26 

393.2 

810.8 

1204.0 

807 

419.56 

393.5 

810.5 

1204.0 

808 

419.85 

393.8 

810.3 

1204.1 

309 

420.15 

394.1 

810.0 

1204.1 

310 

420.45 

394.4 

809.7 

1204.1 

311 

420.76 

394.8 

809.5 

1204.3 

812 

421.06 

395.1 

809.2 

1204.3 

313 

421.35 

395.4 

808.9 

1204.3 

314 

421.65 

395.7 

808.7 

JEZ04.4 

315 

421.94 

396.0 

808.4 

1204.4 

316 

422.24 

396.3 

808.1 

1204.4 

317 

422.53 

396.6 

807.9 

1204.5 

318 

422.82 

396.9 

807.6 

1204.5 

319 

423.11 

397.2 

807.3 

1204.5 

320 

423.40 

397.5 

807.1 

1204.6 

321 

423.69 

397.8 

806.8 

1204.6 

322 

423.97 

398.1 

806.6 

1204.7 

823 

424.26 

398.4 

806.3 

1204.7 

824 

424.54 

398.7 

806.0 

1204.7 

325 

424.83 

399.0 

805.8 

1204.8 

326 

425.11 

399.3 

805.5 

1204.8 

327 

425.40 

399.6 

805.3 

1204.9 

328 

425.69 

399.9 

805.0 

1204.9 

329 

425.97 

400.2 

804.7 

1204.9 

330 

426.26 

400.5 

804.5 

1205.0 

311 

426.54 

400.8 

804.2 

1205.0 

'       332 

426.83 

401.1 

804.0 

1205.1 

333 

427.11 

401.4 

808.7 

1205.1 

334 

427.39 

401.7 

803.5 

1205.2 

335 

427.67 

402.0 

803.2 

1205.2 

836 

427.94 

402.2 

803.0 

1205.2 

284 


TABLE    3. 
Naperian  Logarithms. 

2.7182818  Log    e    =    0.4342945 


=   M. 


.0 

0.0000 

4.1 

.4110 

7.2 

1.9741 

.1 

0.0953 

4.2 

.4351 

7.3 

1.9879 

.2 

0.1823 

4.3 

.4586 

7.4 

2.0015 

.3 

0.2624 

.4 

.4816 

7.5 

2.0149 

.4 

0.3365 

.6 

.5041 

7.6 

2.0281 

.5 

0.4055 

.6 

1.5261 

7.7 

2.0412 

.6 

0.4700 

.7 

1.5476 

7.8 

2.0541 

.7 

0.5306 

.8 

1.5686 

7.9 

2.0668 

.8 

0.5878 

4.9 

1.5892 

8.0 

2.0794 

.9 

0.6418 

6.0 

1.6094 

8.1 

2.0919 

2.0 

0.6931 

6.1 

1.6292 

8.3 

2.1041 

2.1 

0.7419 

5.2 

1.6487 

8.3 

2.1163 

2.2 

0.7884 

5.3 

1.6677 

8.4 

2.1283 

2.3 

0.8329 

5.4 

1.6864 

8.5 

2.1401 

2.4 

0.8755 

5.5 

.7047 

8.6 

2.1518 

2.5 

0.9163 

6.6 

.7228 

8.7 

2.1633 

2.6 

0.9555 

5.7 

.7405 

8.8 

2.1748 

2.7 

0.9933 

5.8 

.7579 

8.9 

2.1861 

2.8 

.0296 

5.9 

.7750 

9.0 

2.1972 

2.9 

.0647 

6.0 

.7918 

9.1 

2.2083 

3.0 

.0986 

6.1 

.8083 

9.2 

2.2192 

3.1 

.1314 

6.2 

.8245 

9.3 

2.2300 

3.3 

.1632 

6.3 

.8405 

9.4 

2.2407 

3.3 

.1939 

6.4 

.8563 

9.5 

2.2513 

3.4 

.2238 

6.5 

.8718 

9.6 

2.2618 

3.5 

.2528 

6.6 

.8871 

9.7 

2.2721 

3.6 

.2809 

6.7 

.9021 

9.8 

2.2824 

3.7 

.3083 

6.8 

1.9169 

9.9 

2.2925 

3.8 

.3350 

6.9 

1.9315 

10.0 

2.3026 

3.9 

1.3610 

7.0 

1.9459 

4.0 

1.3863 

7.1 

1.9601 

TABLE  4. 
Water  Conversion  Factors.* 


TJ.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 
Cubic  inches  of  water  (39.1°) 
Cubic  inches  of  water  (39.1°) 
Cubic  inches  of  water  (39.1°) 
Cubic  feet  of  water  (89.1°) 
Cubic  feet  of   water  (39.1°) 
Cubic  feet   of  water  (39.1°) 
Pounds  of  water 
Pounds  of  water 
Pounds  of  water 

X 

X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 

8.33 
0.13368 
231.00000 
3.78 
0.036024 
0.004329 
0.576384 
62.425 
7.48 
0.028 
27.72 
0.01602 
0.12 

• 

pounds, 
cubic  feet, 
cubic  inches, 
liters, 
pounds. 
U.  S.  gallons, 
ounces, 
pounds. 
U.  S.  gallons, 
tons, 
cubic  inches, 
cubic  feet. 
U.  S.  gallons. 

*  American  Machinist  Hand  Book. 
285 


TABLE    5. 
Volume  and  Weight  of  Wry  Air  at  Different  Temperatures.* 

Under   a   constant   atmospheric   pressure    of   29.92    inches    of 
mercury,   the  volume  at  32°   F.   being   1. 


Tempera- 
ture 

Volume. 

Weight  of 
a  Cubic 

Tempera- 
ture 

Weight  of 
Volume.       a  Cubic 

Fahr. 

Foot. 

Fahr. 

Foot. 

0 

.935 

.0864 

500 

1.954 

.0413 

12 

.960 

.0842 

552 

2.056 

.0385 

221 

.980 

.0824 

600 

2.150 

.0376 

32 

1.000 

.0807 

650 

2.260 

.0357 

42 

1.020 

.0791 

700 

2.362 

.0338 

52 

1.041 

.0776 

750 

2.465 

.0328 

62 

1.061 

.0761 

800 

2.566 

.0315 

72 

1.082 

.0747 

850 

2.668 

.0303 

82 

1.102 

.0733 

900 

2.770 

.0292 

92 

1.122 

.0720 

950 

2.871 

.0281 

102 

1.143 

.0707 

1000 

2.974 

.0268 

112 

1.163 

.0694 

1100 

3.177 

.0264 

122 

1.184 

.0682                    1200 

3.381 

.0239 

132 

1.204 

.0671                    1300 

3.584 

.0225 

142 

1.224 

.0659                   1400 

3.788 

.0313 

152 

1.245 

.0649                   1500 

3.993 

.0202 

162 

1.265 

.0638 

1600 

4.196 

.0192 

172 

1.285 

.0628 

1700 

4.402 

.0183 

182 

1.306 

.0618 

1800 

4.605 

.0175 

192 

1.326 

.0609 

1900 

4.808 

.0168 

202 

1.347 

.0600 

2000 

5.012 

.0161 

212 

1.367 

.0591 

2100 

5.217 

.0155 

230 

1.404 

.0575 

2200 

5.420 

.0149 

250 

1.444 

.0559 

2300 

5.625 

.0142 

275 

1.495 

.0540 

2400 

5.827 

.0138 

300 

1.546 

.0522 

2500 

6.032 

.0133 

325 

1.597 

.0506 

2600 

6.236 

.0130 

350 

1.648 

.0490                   2700 

6.440 

.0125 

375 

1.689 

.0477                    2800 

6.644 

.0121 

400 

1.750 

.0461 

2900 

6.847 

.0118 

450 

1.852 

.0436 

3000 

7.051 

.0114 

*Suplee's  M.  E.  Eeference  Book. 


286 


TABLE   6. 

Weight   of  Pure    Water  per   Cubic    Foot    at    Various 
Temperature.* 


Temp. 
Degrees 
Fahr. 

Weight 
Lbs.  per 
Cu.  Ft. 

B.  t.  u. 
Per  Pound 
above  33. 

Temp. 
Degrees 
Fahr. 

Weight 
Lbs.  per 
Cu.  Ft. 

B.  t.  u. 
Per  Pound 
above  3$. 

32 

62.42 

0.00 

77 

62.26 

45.03 

33 

62.42 

1.00 

78 

63.25 

46.03 

34 

62.42 

2.00 

79 

62.34 

47.03 

35 

62.42 

3.00 

80 

63.23 

48.04 

36 

62.42 

4.00 

81 

62.22 

49.04 

37 

62.42 

5.00 

83 

62.21 

50.04 

38 

62.43 

6.00 

83 

62.20 

51.04 

39 

62.43 

7.00 

84 

62.19 

53.04 

40 

62.42 

8.00 

85 

62.18 

53.05 

41 

62.43 

9.00 

86 

62.17 

54.05 

42 

62.42 

10.00 

87 

62.16 

55.05 

43 

62.42 

11.00 

88 

62.15 

56.05 

44 

62.42 

12.00 

89 

62.14 

57.05 

45 

62.42 

13.00 

90 

62.13 

58.06 

46 

62.43 

14.00 

91 

62.12 

59.06 

47 

62.42 

15.00 

93 

62.11 

60.06 

48 

62.41 

16.00 

93 

62.10 

61.0(5 

49 

62.41 

17.00 

94 

62.09 

62.06 

50 

62.41 

18.00 

95 

62.08 

63.07 

51 

62.41 

19.00 

96 

62.07 

64.07 

52 

62.40 

20.00 

97 

62.06 

65.07 

53 

62.40 

21.01 

98 

62.06 

66.07 

54 

62.40 

22.01 

99 

62.03 

67.08 

55 

62.39 

23.01 

100 

63.02 

68.08 

56 

62.39 

24.01 

101 

62.01 

69.08 

57 

63.39 

25.01 

102 

62.00 

70.09 

58 

62.38 

26.01 

103 

61.99 

71.09 

59 

62.38 

27.01 

104 

61.97 

72.09 

60 

62.37 

28.01 

105 

61.96 

73.10 

01 

62.37 

29.01 

106 

61.95 

74.10 

63 

62.36 

30.01 

107 

61.93 

75.10 

63 

62.36 

31.01 

108 

61.92 

76.10 

64 

62.35 

32.01 

109 

61.91 

77.11 

65 

62.34 

33.01 

110 

61.89 

78.11 

66 

62.34 

34.02 

111 

61.88 

79.11 

67 

62.33 

35.02 

112 

61.86 

80.12 

68 

62.33 

36.02 

113 

61.85 

81.12 

69 

62.32 

37.02 

114 

61.83 

83.13 

70 

62.31 

38.03 

115 

61.83 

83.13 

71 

62.31 

39.02 

116 

61.80 

84.13 

72 

62.30 

40.02 

117 

61.78 

85.14 

73 

62.29 

41.02 

118 

61.77 

86.14 

74 

62.28 

42.03 

119 

61.75 

87.15 

75 

62.28 

43.03 

120 

61.74 

88.15 

76 

62.27 

44.03 

121 

61.72 

89.15 

"Kent's  M.  E.  Pocket-Book. 


287 


Temp. 
Degrees 
Fahr. 

Weight 
Lbs.  per 
Cu.  Ft. 

B.  t.  u.          Temp. 
Per  Pound      Degrees 
above  32.         Fahr. 

Weight 
Lbs.  per 
Cu.  Ft. 

B.  t.  u. 
Per  Pound 
above  32. 

122 

61.70 

90.16 

167 

60.83 

135.43 

123 

61.68 

91.16                 168 

60.81 

136.44 

124 

61.67 

92.17                  169 

60.79 

137.45 

125 

61.65 

93.17 

170 

60.77 

138.45 

120 

61.63 

94.17 

171 

a.  75 

139.46 

127 

61.61 

95.18 

172 

60.73 

140.47 

128 

61.60 

96.18 

173 

60.70                141.48 

129 

61.58 

97.19 

174 

60.68                142.49 

130 

61.56 

98.19 

17» 

60.68   "             143.50 

131 

61.54 

99.20 

176 

60.64                144.51 

133 

61.52 

100.20 

177 

60.62                145.52 

133 

61.51 

101.21 

ITS 

60.59 

146.52 

134 

61.49 

102.21 

179 

60.57 

147.53 

135 

61.47 

103.22 

180 

60.55 

148.54 

136 

61.45 

104.22 

181 

60.53 

149.55 

137 

61.43 

105.23 

182 

60.50 

150.56 

138 

61.41 

106.23 

183 

60.48 

151.57 

139 

61.39 

107.24 

184 

(50.46 

152.58 

140 

61.37 

108.25 

185 

60.44 

153.59 

141 

61.36 

109.25 

186 

60.41 

154.60 

142 

61.34 

110.26 

187 

60.39 

155.  61 

143 

61.32 

111.26 

188 

60.37 

156.62 

144 

61.30 

112.27 

189 

60.34 

157.63 

145 

61.28 

113.28 

190 

60.32 

158.64 

140 

61.26 

114.28 

191 

60.29 

159.65 

147 

61.24 

115.29 

192 

60.27 

160.67 

148 

61.23 

116.29 

193 

60.25 

161.68 

149 

61.20 

117.30 

194 

60.22 

162.69 

150 

61.18 

118.31 

195 

60.20 

163.70 

151 

61.16 

119.31 

196 

60.17 

164.71 

152 

61.14 

120.32 

197 

60.15 

165.72 

153 

61.12 

121.33 

198 

60.12 

166.73 

154 

61.10 

122.33 

199 

60.10 

167.74 

155 

61.08 

123.34 

200 

60.07 

168.75 

156 

61.06 

124.35 

201 

60.05 

169.77 

157 

61.04 

125.35 

202 

60.02 

170.78 

158 

61.02 

126.36 

203 

60.00 

171.79 

159 

61.00 

127.37 

204 

59.97 

172.80 

-160 

60.98 

128.37 

205 

59.95 

173.81 

161 

60.96 

129.38 

206 

59.92 

174.83 

162 

60.94 

130.39 

207 

59.89 

175.84 

163 

60.92 

131.40 

206 

59.87 

176.85 

164 

60.90 

132.41 

209 

59.84 

177.86 

165 

60.87 

133.41 

210 

59.82 

178.87 

166 

60.85 

134.42 

211 

59.79 

179.89 

212 

59.76 

180.90 

288 


TABLE     7. 
Boiling:    Points    of   Water    at    Different    Heights    of   Vacuui 


Temperature 
Fahr. 

Height    of 
Mercury  in 
Vacuum  Tube 
in  Inches. 

Temperature 
Fahr. 

Height   of 
Mercury  in 
Vacuum  Tube 
in  Inches. 

212.0 

0.00 

175.8 

16.00 

210.3 

1.00 

172.6 

17.00 

208.5 

2.00 

169.0 

18.00 

206.8 

3.00 

165.3 

19.00 

204.8 

4.00 

161.2 

20.00 

202.9 

5.00 

156.7 

21.00 

200.9 

6.00 

151.9 

22.00 

199.0 

7.00 

146.5 

23.00 

196.7 

8.00 

140.3 

24.00 

194.5 

9.00 

133.3 

25.00 

192.  2 

10.00 

124.9 

26.00 

189.7 

11.00 

114.4 

27.00 

187.3 

12.00 

108.4 

28.00 

184.6 

13.00 

102.0 

29.00 

181.3 

14.00 

98.0 

29.92 

178.9 

15.00 

TABLE     8. 

Weight    of    Water    With    Air    Per    Cubic    Foot    at    Different 
Temperatures    and    Saturation. 


fc 

fe 

. 

. 

. 

& 

_ 

-M  m 

„ 

4J      ' 

m 

**« 

„ 

-P"  .J 

„ 

-M   .1 

„ 

•*•*  » 

ft 

•a! 

ft 

•gjfl 

ft 

•as 

ft 

•a! 

ft 

a  3 

ft 

•al 

'53  £ 

g 

7T  *c3 

a 

'£  3 

S 

'£  g 

a 

••"«  '^ 

a 

'5  g 

£o 

s 

H 

^o 

& 

£o 

H 

1 

^0 

| 

-20 

0.166 

2 

0.529    1  24 

1.483 

40 

3.539 

68 

7.480 

90 

14.790 

—19 

0.174 

3 

0.554 

35 

1.551 

47 

3.667 

69 

7.726 

91 

15.234 

—18 

0.184 

4 

0.582 

26 

1.623 

48 

3.800 

70 

7.980 

93 

15.C89 

—17 

0.196 

5 

0.610 

37 

1.697 

49 

3.936 

71 

8.240 

93 

16.155 

-16 

0.207 

6 

0.639 

28 

1.773 

50 

4.076 

72 

8.508 

94 

16.634 

—15 

0.218 

7 

0.671 

29 

1.853 

51 

4.222 

73 

8.782 

95 

17.134 

—14 

0.231 

8 

0.704 

30 

1.935 

53 

4.372 

74 

9.  063 

96 

17.626 

—13 

0.243 

9 

0.739 

31 

2.022 

53 

4.526 

75 

9.356 

97 

18.142 

—12 

0.257 

10 

0.776 

32 

2.113 

54 

4.685 

76 

9.655 

98 

18.671 

—11 

0.270 

11 

0.816 

33 

3.194 

55 

4.849 

77 

9.962 

99 

19.213 

—10 

0.285 

13 

0.856 

34 

2.279 

56 

5.016 

78 

10.377 

100 

19.766 

—  9 

0.300 

13 

0.898 

35 

2.366 

57 

5.191 

79 

10.631 

101 

20.335 

—  8 

0.316 

14 

0.941 

S6 

2.457 

58 

5.370 

80 

10.934 

103 

20.^17 

—  7 

0.333 

15 

0.986 

37 

2.550 

59 

5.555 

81 

11.275 

103 

21.   ,4 

—  6 

0.350 

16 

1.032 

38 

2.646 

60 

5.745 

83 

11.626 

104 

22.125 

—  5 

0.370 

17 

1.080 

39 

2.746 

61 

5.941 

83 

11.987 

105 

23.750 

—  4 

0.389 

18 

1.128 

40 

2.8-19 

62 

6.142 

84 

12.356 

106 

23.393 

—  3 

0.411 

19 

1.181 

41 

2.955 

63 

6.349 

85 

12.736 

107 

24.048 

—  3 

0.434 

20 

1.235 

43 

3.061 

64 

6.6C3 

86 

13.127 

108 

24.720 

—  1 

0.457 

21 

1.294 

43 

3.177 

65 

6.782 

87 

13.526 

109 

25.408 

0 

0.481 

23 

1.355 

44 

3.294 

66 

7.009 

88 

13.937 

110 

?6.112 

1 

0.505 

23 

1.418 

45 

3.414 

67 

7.241 

89 

14.359 

289 


TABLE     9. 

Properties    of    Air    With     Moisture    under    Pressure    of 
Atmosphere.  * 


So 

£ 

X) 

Mixtures  of  air  saturated 

§2 

•g 

Q)  O 

>>» 

.2^ 

with  vapor. 

°K 

a 

"flrH 

£ 

CLJ    — 

'"  OS 

S  & 

1 

S^m" 

Weight  of  cubic 

£> 

o>  ~? 

O.S 

O  §1 

^.~  a 

foot  of  the 

ts 

c 
+J 

<w 

^ 

h 

'-3'| 

•^  72 

Cjf§ 

J3*^ 

mixture. 

o 

c* 

S+j 

& 

"So 

*H  ft 
S'l 

"8* 

sis 

-a  . 

a>  ^ 

O  60 

,0 

S-i 

0) 

'3 

"^ 

&B 

£ 

p 

'S03 

Cj^j 

gg 

8|€ 

o.d  n 

^fl 

«g| 

£3 
fcflS 

ci 
t 

s-i  «^ 

«  0 

®S| 

^1 

-D 
Oj 

5^ 

0£ 

O  0) 

«w  g 

-s- 

°  o 
ft 

fl 

'Z'~ 

<M 

^ 

O  k 

^of 

SH          O 

$g 

<3 

*M  'o 

-M  ji> 

o 

O    Q^i(^ 

4J 

4—  *i-H 

0^ 

5° 

ft 

0> 

§5 

to  O 

OJ-*-1  C 

§.2 

Ss 

"3-2 

O 

ofc 

•-'s.S 

2-S 

0) 

H 

>$ 

Is 

^     ft 

i'S 

3  a 
££ 

II 

*».« 

C3  « 

Wfc 

Us 

P  C 
00 

1 

2         3 

4 

5 

6 

7 

8 

9 

10 

31 

12 

0 

.935   nsfii 

0.044 

39.877 

.0863 

.000079 

.086379 

.00092 

1092  40 

48.5 

12 

.960 

.0842 

0.074 

39.849 

.0840 

.000130 

.084130 

.00115 

646  IQi 

50.1 

22 

'.980 

!o824 

0.118 

29!  803 

.0821 

.000202 

1  082302 

.00245 

406.40 

51.1 

32 

1.000 

.0807 

0.181 

29.740 

.0802 

.000304 

.080504 

.00379 

263.81 

3289.0 

52.0 

42 

1.020 

.0791 

0.367 

29.654 

.0784 

.000440 

.078840 

.00561 

178.18 

2252.0 

53.2 

52 

1.041 

.0766 

0.388 

•29.53? 

.0766 

.000627 

.077227 

.00819 

122.17 

1595.0 

54.0 

80 

1.057 

.0764 

0.522 

29.399 

0751 

.000830 

.075252 

.01251 

92.27 

1227.0 

55.0 

62 

1.061 

.0761 

0.556 

29  365 

.0747 

.000881 

.075581 

.01179 

84.79 

1136.0 

56.2 

70 

1.078 

.0750 

0.75-4:29.182 

.0731 

.001153 

.073509 

.01780 

64.59 

88?.  0 

f>7.3 

72 

1.083 

.0747 

.0.785 

29.136 

.0727 

.001221 

.073931 

.01680 

59.54 

819.0 

58.5 

82 

1.103 

.0733 

1.099 

28.82C 

.0706 

.001667 

.072267 

.02361 

42.35 

600-0 

58.7 

92 

1.133 

.0720 

1.501 

38.420 

.0684 

.002250 

.070717 

.03289 

30.40 

444.0 

58.9 

100 

1.139 

.0710 

1.929 

2r.99£ 

.0664 

.0028-18 

.069261 

.04495 

23.66 

356.0 

59.1 

103 

1.143 

.0707 

2.036 

27.885 

.0653 

.002997 

.068897 

.04547 

2]  .98 

334.0 

59.5 

112 

1.163 

.0694 

2.731 

37.190 

.0631 

.003946 

.067042 

.06253 

15.99 

353.0 

60.6 

122 

1.184 

.0682 

3.621 

26.300 

.0599 

.005142 

.065046 

.08584 

11.65 

194.0 

61.7 

132 

1.204 

.0671 

4.752 

25.169 

.0564 

.OC6639 

.063039 

.11771 

8.49 

151.0 

62.5 

142 

1.224 

.0660 

6.165 

23.756 

.0534 

.008473 

.060873 

.16170 

6.18 

118.0 

63.7 

152 

1.245 

.0649    7.930 

21.991 

.0477 

.010710 

.058416 

.22465 

4.45 

93.3 

65.0 

162 

1.265 

.0638 

10.099 

19.823 

.0423 

.013415 

.055715 

.31713 

3.15 

74.5 

66.1 

172 

1.285 

.0628 

12.758 

17.163 

.0360 

.016682 

.052682 

.46338 

2.16 

59.2 

67.1 

182 

1.306 

.0618115.960 

13.961 

.0288 

.020536 

.049336 

.71300 

1.402 

48.6 

68.0 

192 

1.326 

.06Q9;19.828 

10.093 

.0205 

.025142 

.045642 

1.22643 

.815 

39.8 

68.9 

202 

1.347 

.0600 

24.450 

5.471 

.0109 

.030545 

.041445 

2.80230 

.357 

82.7 

70.2 

212 

1.367 

.0591 

29.931 

0.000 

.0000 

.038820 

.036320 

finite 

.000 

27.1 

71.4 

"Carpenter's  H.  &  V.  B.  and  Sturtevant's  Mech.  Draft. 


290 


(I) 
Q 

s  i 

I  i 

hi 


21     S 


«  155 


niiiiiiiiiiiiiiiiiiiiii 


291 


TABLE    11. 
Fuel  Value  of  American  Coals.* 


COAL, 
Name   or  Locality. 

Fuel  Value  per  Pound 
of  Coal. 

B.  t.u. 
calculated. 

B.'t.u.  by 
calorimeter. 

Theoretical  evap- 
oration in  Ibs. 
from  and  at 

212  °F 

ARKANSAS. 
Spadra,    Johnson    Co 

14,420 

9,215 

13,560 
8,500 

14,020 
13,097 

14,391 
15,198 
9,326 

13,714 
13,414 

14,199 
13,300 

14,200 

11,813 
11,756 

11,781 
9,035 
9,739 
13,123 

8,703 

9,890 
11,756 

13,104 
12,936 

9,450 
12,963 

14,373 

14.90 
12.23 
12.17 
9.54 

14.04 
8.80 

13.19 
9.35 
10.09 
13.68 

14.50 
13.56 

9.01 

14.89 
16.76 
9.65 

10.24 
13.17 

14.30 
13.90 

14.70 
12.73 
13.46 
13.39 

9.78 
13.41 

14.71 
14.70 

Coal  Hill,  Johnson  Co. 

Huntington  Co. 

Lignite    _ 

COLORADO. 
Lignite    

Lignite    slack 

ILLINOIS. 
Big    Muddy,    Jackson    Co  

Colchester,    Slack 

Giliespie,    Macoupin    Co. 

Mercer  Co. 

INDIANA. 
Block 

Cannel  .      

IOWA. 

Good  cheer 

KENTUCKY. 
Caking    _       __       

Cannel  

Lignite    

MISSOURI. 
Bevier    Mines   

NEW  MEXICO. 
Coal 

OHIO. 
Briar   Hill,    Mahoning    Co. 

Hocking    Valley 

PENNSYLVANIA. 
Anthracite    

Anthracite,   pea  

Pittsburgh  (average)  

Youghiogheney 

TEXAS". 

Port   Worth 

Lignite 

WEST  VIRGINIA. 
Pocahontas     —  

New  River                       —             _  __    _ 

*Sturtevant's  "Mechanical  Draft." 


292 


TABLE    12. 
Capacities  of  Chimneys,* 


Inside  Diameter  of 
Lined  Flue 
(Inches) 

Maximum  Sq.    Ft.   of  Cast-iron  Radiating 
Surface  and  B.   t.   u.   for  a   Flue  of  the 
Given  Diameter  and  Height. 

| 

W 

,cj 

to 

i 

a 

be 

5 

i 

W 

,a 
&o 

a 

i 
w 

3 

& 

3 

3 

00 

§ 

6 
7 
8 
9 
10 
12 
15 
18 

Steam    

146 
243 

36500 

228 
379 

57000 

327 
544 

81750 

445 
742 
111250 

582 
969 
145500 

909 
1514 
227250 

1537 
2561 

334250 

2327 

3878 
581750 

175 
291 

43750 

273 
455 
68250 

392 
653 

98000 

534 
890 
133500 

698 
1163 

174500 

1090 
1817 

272500 

1844 
3073 
461000 

2792 
4653 
698000 

204 

340 
51000 

319 
531 

79750 

457 

763 
114250 

623 
1038 
155750 

814 
1357 
203500 

1272 
2120 
318000 

2151 

3586 
537750 

3257 
5429 
814250 

233 

388 
58250 

364 

607 
91000 

523 
871 

130750 

712 

1187 

178000 

930 
1551 

232500 

1454 
2423 
363500 

2458 
4098 
614500 

3722 
6204 
930500 

262 
437 
65500 

410 
683 
102500 

588 
980 
147000 

801 
1335 
200250 

1047 
1745 
261750 

1636 
2726 
409000 

2766 
4610 
691500 

4188 
6980 
1047000 

291 

485 
72750 

455 

758 
113750 

653 

1088 
163250 

890 
1483 

222500 

1163 
1938 
290750 

1817 
3028 
454250 

3073 
5122 

768250 

4653 
7755 
1163250 

Hot    Water  
B.  t.  u.  ___ 

Steam   _.  _ 

Hot    Water  

B.  t.  u.  _    _  _    — 

Steam    

Hot    Water  . 

B.  t.  u.  ___  _ 

Steam    

Hot    Water  

B.  t.  u.  

Steam 

Hot    Water 

B.  t.  u. 

Steam 

Hot    Water  
B.  t.  u. 

Steam    _-.___ 

Hot    Water  
B.  t.  u. 

Steam   _ 

Hot    Water.  __ 
B.  t.  u  - 

Radiation  is  calculated  at  250  B.  t.  u.  steam,  150  B.  t.  u.  water. 


*The  Model  Boiler  Manual. 


293 


TABLE    13. 
Equalization    of     Smoke    Flues— Commercial 


Inside 
Diameter 
Lined  Flue 

Brick  Flue 
Not  Lined 
Well  Built 

Rectangular 
Lined  Flue 
Outside  of  Tile 

Outside 
Iron 
Stack 

6 
7 
8 
9 
10 
13 
15 
18 

8%x8% 

8y2x8y2 
8y2x8y2 

8V2xl3 
8y2xl3 
13x13 
13x17 
17x21  %j 

7x7 
8y2x8y2 
8^x13 
8V2X13 
13x13 
13x18 
18x18 

8 
9 
10 

11 

12 
14 
17 
20 

Round  Flue  Tile  Lining1  is  listed  by  its  inside  measurement. 
Rectangular  Lining1  by  outside  Measurement. 

TABLE   11 
Dimensions   of  Registers.* 


Size  of 
opening, 
Inches 

Nominal 
area  of 
opening, 
Square 
Inches 

Effective 
area  of 
opening, 
Square 
Inches 

Tin  Box  Size, 
Inches 

Extreme 
dimensions  of 
register  face, 
Inches 

6x10 

60 

40 

63 

'•  x  10T95 

7jl  x  lljj 

8x10 

80 

53 

85 

i  x  10H 

8x12 

96 

64 

/8  X  12% 

9%  x  13K 

8x15 

120 

80 

85 

8  X  15% 

9K  x  1615 

9x12 

108 

72 

91 

5  x  12JS 

IOH  x  13% 

9x14 

126 

84 

9] 

4  x  14H 

10%  x  16# 

10x12 
10x14 
10x16 

120 
140 
160 

80 
93 
107 

1014  x  I2\l 
101J  x  1614 

llli  x  1318 
1118  x  1518 
1118  x  17% 

12x15 

180 

120 

123 

4x15% 

14^  x  17 

12x19 

228 

152 

12; 

14^  x  21 

14x22 

308 

205 

14, 

4  x  22% 

16*4  x  24^ 

15x25 

375 

250 

15, 

/sx25% 

16x20 

320 

218 

16 

ft  x  20% 

18T5S  x  22A 

16x24 

384 

256 

16, 

ft  x24% 

ISA  x  22& 

20x20 

400 

267 

2018  x  2018 

22%  x  22% 

20x24 

480 

820 

20, 

8  x  241  i 

22%  x  26% 

20x26 

520 

347 

20 

8  x  2618 

22%  x  28% 

21x29 

609 

403 

21 

8  x  2918 

28%  x  81% 

27x27 

729 

486 

27- 

8x2718 

29%  x  29% 

27x38 
80x30 

1026 
900 

684 
600 

27- 
80 

8x3818 
8  x  3018 

29%  x  403/g 
32%  x  32% 

Dimensions  of  different  makes  of  registers  vary  slightly,    Th 
above  are  for  Tuttle  &  Bailey  Manufacturing  Oo.'s  manufacture. 

*The  Model  Boiler  Manual. 


£94 


TABLE    15. 

Specific  Heats,  Coefficients  of  Expansion,  Coefficients  of  Trans- 
mission, and  Fuslng-Points  of  Solids,  Liquids  or  Gases.* 


SUBSTANCE. 

o 

2* 

C>  5? 

«jM 

Coefficient  of 
Expansion. 

Coefficient  of 
Transmission 

Fusion  Points 
Degrees 

Antimony 

0.0508 
0.0951 
0.0324 
0.1138 
0.1937 
0.1298 
0.0314 
0.0324 
0.0570 
0.0562 
0.1165 
0.1175 

.00000602 
.00000955 

.00001060 
.00000895 
.00000478 
.00000618 
.00001580 
.00000530 
.00001060 
.00001500 
.00000600 
.00000689 
.00000003 
.00001633 
.00001043 
.00000375 
.00006413 
.00007860 
.00002313 
.00012530 
.00006806 
.00003333 
.00015151 

.00022 
.00404 

815 

1949 
1947 
2975 
1832 
2192 
621 
3452 
1751 
446 
2507 
2507 

"787 
1859 
32 

Copper 

Gold                   .    — 

Wrought    Iron    
Glass        

.00089 
.0000008 
.000659 
.00045 

Cast  Iron  

Lead 

Platinum 

Silver 

.00610 
.00084 
.00062 
.00034 

Tin                       .    — 

Steel   (soft)   

Steel    (hard)    

Nirkel   steel   36% 

Zinc 

0.0956 
0.0939 
0.5040 
0.2026 
0.2410 
0.1970 
0.1887 
1.0000 
0.0333 
0.7000 

.00170 
.00142 
.000024 

"660602 

.00203 

"ooooos 

.00011 
.000000 

Brass 

Ice 

Sulphur               

Charcoal 

1213 

Aluminum    _ 

Phosphorus        

Water             

Mercury 

:::: 

Alcohol    (absolute) 

Con- 
stant 
Pres- 
sures 

Con- 
stant 
volume 

Coefficient 
of  cubical  ex- 
pansion at  1 
atmos. 

Air 

0.23751 
0.21751 

3.40900 
0.24380 
0.4805 
0.2170 

0.16847 
0.15507 
2.41226 
0.17273 
0.346 
0.1535 

.003671 
.003674 
.003669 
.003668 
.003726 

.0000015 

.0000012 
.0000012 
.0000012 

"60006120 



Oxygen 

Hydro  gen 

Nitrogen 

Superheated    Steam 
Carbonic  Acid   

"Kent  and  Suplee. 


295 


TABLE    16. 


Capacities  of  \Varm  Air  Furnaces  of  Ordinary  Construction 
Cubic  Feet  of  Space  Heated.* 


Divided  Space 

Fire  Pot 

Undivided  Space 

+10° 

0° 

—10° 

Diam. 

Area 

+  10° 

0° 

-10° 

12000 

10000 

8000 

18  in. 

1.8  sq.  ft. 

17000 

14000 

12000 

14000 

12000 

10000 

20 

2.2 

22000 

17000 

14000 

17000 

14000 

12000 

22 

2.6 

26000 

22000 

17000 

22000 

18000 

14000 

24 

3.1 

30000 

-26000 

22000 

26000 

22000 

18000 

26 

3.7 

85000 

30000 

26000 

30000 

26000 

22000 

28 

4.8 

40000 

35000 

30000 

35000 

30000 

26000 

30 

4.9 

50000 

40000 

35000 

TABLE    17 
Capacities    of    Hot-Air    Pipes    and    Registers. 


^ 

fl  f-> 

«M-t->£j 

£ 

a 

h 

<U 

'"-$ 

°  ^ 

o 

0 

la 

2 

13 

« 

• 

'§ 

*""* 

CJ  ^  C) 

ft  o 

• 

1 

a  t-> 

S** 
^ 

«w  o  9 

*5 

«H  0 

R 

•2  ° 

3 

53 

O 

«w 

"eS  & 

09 

c 

1 

III 

H  80, 

>  £  . 

Ill 

O  cc^  js 

5iD 
S 

11 

6x8 

6  in. 

4x8 

400 

450 

500 

8x8 

7    " 

4x10 

450 

500 

560 

8x10 

8    " 

4x10 

500 

850 

880 

8x13 

8   " 

4x11 

800 

1000 

1050 

9x13 

9    "                     4x12 

1050 

1250 

1324 

9x14 

9   " 

4x14 

1050 

1350 

1450 

10x13 

10   " 

4x14 

1500 

1650 

1800 

10X14 

10   " 

6x10 

1800 

2000 

2200 

10x16 

10   " 

6x10 

1800 

2000 

2200 

12x14 

12    " 

6x12 

2200 

2300 

2500 

12x15 

12   " 

6x12 

2250 

2300 

2500 

12x17 

12    " 

6x14 

2300 

2600 

2800 

12x19 

12    " 

6x14 

2300 

2600 

2800 

14x18 

14   " 

6x16 

2800 

3000 

3200 

14x20 

14   " 

6x16 

2900 

3000 

3200 

14x22 

14    " 

8x16 

3000 

3200 

3400 

16x20 

16    " 

8x18 

3600 

4000 

4250 

16x24 

16   " 

8x18 

3700 

4000 

4250 

20x24 

18    " 

10x20 

4800 

5400 

5750 

20x26 

20   " 

10x24 

6000 

7000 

7450 

•Federal  Furnace  League  Handbook. 
tKidder's  Arch  and  B'ld'rs  Poclcet-Book. 

296 


TABLE    18. 
Air  Heating:  Capacity  of  Warm  Air  Furnaces.* 


Fire  Pot 

Casing 

Total  cross 
sec.  area  of 
heat  pipes 

No.  and  size  of  heat  pipes  that 
may  be  supplied 

Diam. 

Area 

Diam. 

18  i 
20 

i. 

1.8  iq. 

2.2    * 

ft. 

30"-32" 
34"-36" 

180  sq 

280 

(in. 

3-9"  or  4-8" 
2-10"  and  2-9"  or  3-9"  and  2-8" 

22 

2.6 

86'  '-40" 

360 

3-10"  and  2-9"  or  4-9"  and  2-8" 

24 

3.1 

4011.4411 

470 

3-10",  1-9"  and  2-8"  or  2-10"  and  5-8" 

26 

3.7 

44"-50"  565 

5-10   and  3-9   or  3-10  ,  4-9   and  2-8 

28 

4.3 

48"-56" 

650 

2-12  ,  3-10   and  3-9   or  5-10  ,  3-9   and  2-8 

30 

4.9 

52'  '-60" 

730 

3-12  ,3-10  and  3-9  or  5-  10  ,5-9  and    1-8 

TABLE   19. 

Sectional  Area  (Sq.  Inches)  of  Vertical  Hot  Air  Flues,  Natural 
Draft,  Indirect  System.f 

Outside  Temjperature  50°  F.     Flue  Temperature   90°  F. 


STEAM 

WATER 

Sq.  Ft. 

Cast-  Iron 

Radiation 

rd 

^ 

<O 

,- 

^ 

O  f-i 

"Sb 

tJ>» 

mtt 

0^ 

2b 

•££? 

£  O 

33 

0° 

S° 

o  o 

2£ 

§-2 

faze 

O2O2 

HflQ 

fa72 

Vll/1 

faO2 

0  to    50 

TOO 

75 

63 

60 

75 

63 

60 

60 

60          75 

150 

113 

94 

80 

113 

94 

80 

80 

75        100 

200 

150 

125 

100 

150 

125 

100 

100 

100        125 

250 

188 

156 

125 

188 

156 

125 

125 

12o        150 

300 

225 

188 

150 

225 

188 

150 

150 

150        175 

350 

263 

219 

175 

263 

219 

175 

175 

175        200 

400 

300 

250 

200 

300 

250 

200 

200 

200        225 

450 

338 

281 

225 

338 

281 

225 

225 

225        250 

500 

375 

313 

250 

375 

313 

250 

250 

250        275 

550 

413 

344 

275 

413 

344 

275 

275 

275        300 

600 

450 

375 

300 

450 

375 

303 

300 

300        325 

650 

488 

406 

325 

488 

406 

325 

325 

325        350 

700 

525 

438 

350 

525 

438 

350 

350 

350        375 

750 

563 

469 

375 

563 

469 

375 

375 

375        400 

800 

600 

500 

400 

600 

500 

400 

400 

Velocity 
Feet   Per   Sec. 

* 

« 

* 

* 

1% 

« 

4 

4 

Effective  Area 

of  Register 

1.00 

1.50 

1.83       2.17        1.00 

1.00 

1.33 

1.33 

Factor  for 

*Federal  Furnace  League  Handbook. 
tThe  Model  Boiler  Manual. 


297 


TABLE   20. 


Pressure,     in     Ounces,     per     Square     Inch     Corresponding    to 
Various  Heads  of  Water,  in  Inches.* 


Decimal  Parts  of  an  Inch. 

Head 

in 

inches. 

.0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

0 

.06 

.12 

.17 

.23 

.29 

.35 

:40 

.46 

.52 

1 

.58 

.63 

.69 

.75 

.81 

.87 

.93 

.98 

1.04 

1.00 

2 

1.16 

1.21 

1.27 

1.33 

3.39 

1.44 

1.50 

1.56 

1.62 

1.67 

3 

1.73 

1.79 

1.85 

1.91 

1.96 

2.02 

2.08 

2.14 

2.19 

2.25 

4 

2.31 

2.37 

2.42 

2.48 

2.54 

2.60 

2.66 

2.72 

2.77 

2.83 

6 

2.89 

2.94 

3.00 

3.06 

3.12 

3.18 

3.24 

3.29 

3.3J 

3.41 

6 

3.47 

3.52 

3.58 

3.64 

3.70 

3.75 

3.81 

3.87 

3.92 

3.98 

7 

4.04 

4.10 

4.16 

4.221 

4.28 

4.33 

4.39 

4.45 

4.50 

4.56 

8 

4.62 

4.67 

4.73 

4.79 

4.85 

4.91 

4.97 

5.03 

5.08 

5.14 

9 

5.20 

5.26 

5.31 

5.37 

5.42 

5.48 

5.54 

5.60 

5.66 

5.72 

TABLE    21. 

Height  of  Water  Column,  in  Inches   Corresponding  to  Pres- 
sures, in  Ounces,  per  Square   Inch.* 


Pressure 
in    ounces 


Decimal  Parts  of  an  Ounce. 


±>^±     Q\J14O..LC; 

inch. 

.0 

,1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

0 

.17 

.35 

.52 

.69 

.87 

1.04 

1.21 

1.38 

1.56 

l 

1.73 

1.90 

2.08 

2.25 

2.42 

2.60 

2.77 

2.94 

3.11 

3.29 

2 

3.48 

3.63 

3.81 

3.98 

4.15 

4.33 

4.50 

4.67 

4.84 

5.01 

3 

5.19 

5.36 

5.54 

5.71 

5.88 

6.06 

6.23 

6.40 

6.57 

6.75 

4 

6.92 

7.09 

7.27 

7.44 

7.61 

7.79 

7.96 

8.13 

8.30 

8.48 

5 

8.65 

8.82 

9.00 

9.17 

9.34 

9.52 

9.69 

9.86 

10.03 

10.21 

6 

10.38 

10.55 

10.73 

10.90 

11.07 

11.26 

11.43 

11.60 

11.77 

11.95 

7 

12.11 

12.28 

12.46 

12.63 

12.80 

12.97 

13.15 

13.32 

13.49 

13.67 

8 

13.84 

14.01 

14.19 

14.36 

14.53 

14.71 

14.88 

15.05 

15.22 

15.40 

9 

15.57 

15.74 

15.92 

16.09 

16.20 

16.45 

16.62 

16.70 

16.96 

17.14 

*Suplee's  M.  E.  Reference  Book. 


298 


JOO  j 


M  0  j^  9 


MrtrHiHrHiHrHiHCOWOOCOOOOOWCOGOOOOOOOOOOOOOOOOOOO 


jooj   lad 


looj  Diqno 


13 


~   - 

i  S  co  3> ' 


•*  tt  M  *»  8>  1-4  r-l  IH 


bS 


Oi  <?i  CO  fc-  ' 

-^  &  o  GQ 


U 


t~  O  C<>   C^  Ci  CO  rH 


•xoaddy 


299 


TABLE    23. 
Expansion  of  Wrought-Iron  Pipe  on  the  Application  of  Heat.* 


Tern  p.  Air 

When 

Pipe 

is  Fitted. 


Increase  in  Length  in   Inches  Per  100  Feet 
When  Heated  to 


Degrees 

160 

180 

200 

212 

220 

228 

240 

274 

Fahr. 

0 

1.28 

1.44 

1.60 

1.70 

1.76 

1.82 

1.93 

2.19 

32 

1.02 

1.18 

1.34 

1.44 

1.50 

1.57 

1.66 

1.94 

50 

.88 

1.04 

1.20 

1.30 

1.36 

1.42 

1.52 

1.79 

70 

.72 

.88 

1.04 

1.14 

1.20 

1.26 

1.36 

1.63 

TABLE    24. 
Tapping:   List   of  Direct   Radiators.f 

STEAM. 


ONE-PIPE  WORK. 

TWO-PIPE   WORK. 

Radiator  Area. 
Square  Feet. 

Tapping  Diam- 
eter.   Inches. 

Radiator  Area. 
Square  Feet. 

Tapping  Diam- 
eter.   Inches. 

0—  24 
24—   60 
60  —  100 
100  and  above 

1 

l!4 

I* 

0  —  48 
48  —  96 
96  and  above 

1    x  % 
114x1 
l%xl% 

WATER. 
Tapped  for*  Supply  and  Return. 


Radiator   Area. 
Square  Feet. 

Tapping    Diameter. 
Inches. 

0  —  40 
40  —  72 
72  and  above. 

1 
VA 

1% 

*Holland  Heating  Manual, 
t American  Radiator  Co. 


300 


TABLE    25. 
Pipe  Equalization. 


This  table   shows  the  relation  of  the 

combined  area  of  small  round  warm  air  w  ,-<  <*  eo  M  us  us  *>  «  * 

ducts  or   pipes   to    the   area  of   one  ^  £*!«»»£  2S^ 

large  main  duct.  S^2  rn'rHiHiHiH  rH^e* 

The  bold  figures  at  the  top  of  the  ,_  H  <s  «  >*  us  <o  t-  cs  o  «-j  « 

column  represent  the  diameters  ^^^^  ^^^^^  ««« 

,.          ,  r    11  «OrH«eO^    iO«D«5<3Sr-l    «  CO  « 

of    the    small  pipes    or    ducts;  ^^^^^^^^^eiwd** 

those  in  the  left-hand  vertical  ^e^ust-cco^^co 

columns  are  the  diameters  of  "rn'r-l^r-iMM^ciwdoid&i 

the  main  pipes.     The  small  ^  *-;  e*coin«ot>  os  <=>«>*  us  t-osr-i 

figures    show   the  number  ~£  *&$*  ***** 

of  small  pipes    that  each  S_;_;  ^  ^  ,_;  .H'  .-J  «te»c4«te» 
main   duct    will  supply. 

„  ,  _.  ,. 

h.xample.  —  1  o  supply  six- 
teen  10-inch  pipes:     Refer 

to  column  having  10  at  top;  e  ^eo^ob:  esrHtoia®  smuat^e  wooq 

follow    down    to    small  "^  IH  I-H  r4  rn  ^  McioJoid  ««««>*  ^^^ 

ficure  1  6  thence  left  on  £  »1  *.<*  ®.  *.®  «.**  ®.  °!  ®.  **:*.'»  ®.  ^  »  ^ 

iiguic  i  y,  ui    iicc  icu  on  t~rHrHrnrHrHc4e«&Jc4WM<>i«ieo^^«ivft'£> 

the  horizontal  line  or  e3«co^t-oorHc4iot--oMcooj«-*Qqi» 

the  bold-face  figure  —  IH  rn  rn'M^dsi  «<SMWM  co^^^ui 

in  the  outside  col-  ^  K-  "  ^  ®.  »  'I  ^.  »  °J  1  ^  »  ^  ^  °?  «*.  *.  ^ 

j       c  j  *•  t-i  i-i  rJ  rJ  IH  •»  «  «i  oi«»  e»  w  •*  ^T"*  »e  »o  « 

umn,  and  we  find  ^  «  so  10  1-  o  «  •*  o»  IH  •*  «o  r-j  ^*  t-  rn  i>  o  •*  i-j 

that  one  30-inch  •-  r4  »4i4  IH  «  «  ei  e«  eo  ««'*'*-*  uj  10  to  «o  i>  z>  t>  ed 

mam  will  sup-  m  e>i  •»*  «&  oq  r-j  eoiDCONio  ocooooit-  T-J  us  i-j  so  <* 

ply   air    for  ^THrHrHrHd«»<^e4eoeo'*-*'*io>o«oeDi>»>a3 

«*•«    "*OO3C4i«    COrH^OOlS    t-  T-)  b-  «  t-    "HOiOrHO 

the  sixteen                                —  ^  H  t4  r40j  «  «  co  eo  «  <*  -*  10  ia  «5  co  ^  06  06  d  M 

1  0  -  inch                                M**^  t-o«o«ooi  cQt>r-HO«  i>  r-j  oq  »«  e  "^^SSS 

oioes                                         ''"'"^rH  iHcie^ei^i  coM-<f!-*ia  ta  <>  <D  t>  ad  ooos 

c^  c*  'ft  co  r-j-^oqe^o  i-jvisot--^  as  »o  so  IH  os  OI-HNSO-*  oooo 

*~iHrH,_;  Nuieicoeo'  rji^ujiaco  «6i>o6osc>  ^ 

^_  e<i  us  co  K  ®  s»  -*  o»  us  6Je-<»«DO  es  ©  o  TH  «  »^us®eo  ggg^ 
*"  rt  r4  ?H  <(J                                                       1"1' 

0  «  «D  os  »s  co 

^-    ^  ^  ^  (jj  («4    CO  CO  •*  US  ITS    O  Z>  t- 

co   t><SU50O  NOsi>u5rij  -*cO 

01  rH    T-ieifiievSCO    -^Wiu5«Ot>    00(35 

«b-  N»^rHoq  t-cot-.eocs  oco 

*",_,,_,     (jJoiCOrJH^     USCOt-0001 

« 
i-i  IH  04  coco^ioo  j>  a> 

us 

IH 

»«. 

t-H  «  CO  •*  US    t-  OS 

ss^  c?c5^^S  g££SS;  IgSSS  ISI1I  I 

i^s  s^^sg  mil  iii|S  ig|||  | 

lllil 


S2*SS  51 

^t- m   to  i— oo  CD  o   «-  « 


SSSS 


301 


TABLE    26. 


Capacities    of    Hot    \Vater    Risers    in    Square    Feet    of    Direct 
Radiation.* 

Drop    in    Temperature    20°. 


D.    of 

Riser 

1  F'l. 

2  PI. 

3  Fl. 

4  Fl. 

5  Fl. 

6  Fl. 

Inches. 

% 

32 

IT 

21 

24 

] 

22 

32l 

40 

48 

i*/i 

38 

56 

70 

80 

88 

iy2 

66 

92 

113 

132: 

-145 

2 

140 

196 

238 

280 

310 

2*A 

240 

328 

400 

470 

515 

3 

350 

490 

595 

700 

770 

850 

m 

510 

705 

860 

1010 

1110 

1215 

4 

700 

980 

1190 

1280 

1540 

1660 

A  small  pipe  should  never  be  run  to  a  great  height  where  it 
only  supplies  one  radiator.  It  is  better  to  have  limits  for  pipes 
as  follows: 


D    in   inches: 

Height   in   feet: 


45 


(Reduce   size    by 
floors.) 


TABLE    27. 
Capacities  of  Pipes  in  Square  Feet  of  Direct  Steam  Radiation. 


£ 

3 

§ 

i 

1 

£ 

C3 

•  ij 

g-^g® 

02 

03 

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a«(N 

w 

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ej  o  a^ 

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03*0  G*§ 

cj  G+J'O 

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5   esS 

CO 

1C 

Q    ai5 

Q      Ccj  H^ 

c* 

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1 

l 

36 

60 

5 

3M, 

3720 

6200 

1^4 

i 

72 

120 

6 

sy% 

6000 

10000 

1% 

1% 

120 

200 

7 

4 

9000 

15000 

2 

i^ 

280 

480 

8 

4 

12800 

21600 

S% 

2 

528 

880 

9 

4% 

17800 

30000 

3 

2% 

900 

1500 

10 

5 

23200 

39000 

3^ 

8% 

1320 

2200 

12 

6 

37000 

62000 

4 

3 

1920 

3200 

14 

7 

54000 

92COO 

*K 

3 

2760 

4600 

16 

8 

76000 

130000 

international  Correspondence  School. 
tKent's  M.  E.  Pocket-Book. 


302 


TABLE    28. 

Capacities    of    Hot    Water    Pipes    in    Square    Feet    of    Direct 
Radiation.* 


JHJ 

Q^JS 

Indirect 
Radial'  n 

Direct  Radiation.     Height  of  Coil  above  bottom  of  boiler,  in  ft. 

0 

10 

'    20 

30 

40 

50 

70 

100 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

3q.  ft. 

% 

49 

50 

62 

53 

55 

57 

61 

68 

1 

87 

89 

93 

95 

98 

101 

108 

121 

144 

]36 

140 

144 

149 

153 

158 

169 

189 

i1^ 

196 

20;: 

209 

214 

222 

228 

243 

271 

2 

349 

359 

370 

380 

393 

405 

433 

483 

•tt 

546 

561 

577 

595 

613 

633 

678 

755 

3 

785 

807 

835 

856 

888 

912 

974 

1086 

3% 

1069 

1099 

1133 

1166 

1202 

1241 

1327 

1480 

4 

1395 

1436 

1478 

1520 

1571 

1621 

1733 

1933 

4V2 

1767 

3817 

1871 

1927 

1988 

2052 

2193 

2445 

5 

3185 

2244 

2309 

2876 

2454 

2531 

2713 

3019 

6 

3140 

3228 

3341 

3424 

3552 

3648 

3897 

4344 

7 

4276 

4396 

4528 

4664 

4808 

4964 

5308 

5920 

8 

5580 

5744 

5912 

6080 

6284 

6484 

6932 

7735 

9 

7068 

7268 

7484 

7708 

7952 

8208 

8774 

9780 

10 

8740 

8976 

9236 

9516 

9816 

10124 

10852 

12076 

11 

10559 

10860 

11180 

11519 

11879 

12262 

13108 

14620 

13 

12560 

12912 

13364 

13696 

14208 

14592 

155S8 

17376 

13 

14748 

15169 

15615 

16090 

16591 

17126 

18307 

20420 

14 

17104 

17584 

18109 

18656 

19232 

19856 

21232 

23680 

15 

19634 

20195 

20789 

31419 

22089 

22801 

24373 

27168 

16 

22320 

22978 

23643 

24320 

25136 

25936 

27728 

30928 

TABLE 
Capacities    of    Hot    \Vater    Mains 
Radiatioi 

29. 
iii 

i.t 

Square 

Feet 

of 

Direct 

D.  of 
mains  . 

Total 

Estimated 

Length 

of 

Circuit. 

100 

200 

300 

400 

500 

600 

700 

800 

900 

1000 

1 

20 

1% 

35 

20 

1% 

56 

40 

25 

2 

116 

85 

70 

50 

VA 

220 

150 

120 

100 

90 

s 

345 

240 

SCO 

170 

150 

140 

125 

110 

100 

90 

3V2 

500 

340 

280 

245 

225 

205 

190 

175 

162 

150 

4 

700 

485 

390 

340 

310 

280 

260 

240 

230 

220 

4% 

925 

640 

535 

460 

410 

37f 

345 

325 

300 

295 

5 

1200 

830 

700 

600 

540 

490 

450 

420 

400 

380 

6 

1900 

1325 

1100 

960 

850 

775 

700 

650 

620 

600 

7 

2000 

1600 

1400 

1250 

1140 

1050 

975 

925 

875 

8 

1970 

1720 

1550 

1440 

1350 

1300 

1260 

9 

1900 

1800 

1700 

1620 

*Kent's  M.  E.  Pocket-Book. 
{International  Correspondence  School. 

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rH<N  Tt<  5OQO     • 


CO  b-  ^ 


CM 


^t- 

3<|  •«<  t-  i—  1  IO  O 


oooo 

CO  •*  10  «0  t 


306 


TABLE  33. 
Expansion    Tanks — Dimensions    and    Capacities.* 


Size  in  Inches 

Capacity  Gallons 

Sq.  ft.  of  Radiation 

9x20 

6% 

150 

10x20 

8 

250 

12x20 

10 

350 

12x24 

12 

450 

12x30 

15 

550 

12x36 

18 

650 

14x30 

20 

700 

14x36 

24 

850 

16x30 

26 

900 

16x36 

32 

1250 

16x48 

42 

1750 

18x60 

66 

2750 

20x60 

82 

4500 

22x60 

100 

6000 

24x60 

122 

7500 

TABLE  34. 
Fr,ee  Areas  Through  Vento  Heaters.     Regular  Adjustments.! 


40-Inch    Section 

50-Inch  Section 

60-Inch    Section 

11.5  sq.   ft.   per  sec. 

14  sq.  ft.  per  sec. 

17  sq.  ft.  per  sec. 

depth  of  sec.  9  in. 

depth  of  sec.  9  in. 

depth  of  sec.  9  in. 

cJ    . 

•05 

a)  ij 

03 

<£>  +j 

03 

s* 

3 

•^  2} 

-—     r/l 

q 

^   <1> 

rt    fa 

a 

fll 

~  03 

o 

8* 

4->    A\ 

S| 

o 

8  . 

"|.§ 

o 

CJ 

1 

33 

1 

££ 

35 

9 

VI 

faM 

35 

7 

4.34 

35 

7 

5.37 

35 

7 

6.45 

35 

8 

4.96 

40 

8 

6.14 

40 

8 

7.37 

40 

9 

5.58 

45 

9 

6.91 

45 

9 

8.29 

45 

10 

6.20 

50 

10 

7.68 

50 

10 

9.21 

50 

11 

6.82 

55 

11 

8.45 

55 

11 

10.13 

55 

12 

7.44 

60 

12 

9.22 

60 

12 

11.05 

60 

18 

8.06 

65 

13 

9.99 

65 

13 

11.97 

65 

14 

8.68 

70 

14 

10.76 

70 

14 

12.89 

70 

15 

9.30 

75 

15 

11.53 

75 

15 

13.81 

75 

36 

9.92 

80 

16 

12.30 

80 

16 

14.73 

80 

17 

10.54 

85 

17 

13.07 

85 

17 

15.65 

85 

18 

11.16 

90 

18 

13.84 

90 

18 

16.57 

90 

19 

11.78 

95 

19 

14.59 

95 

19 

17.50 

95 

20 

12.40 

100 

20 

15.36 

100 

20 

18.42 

100 

*The  Model  Boiler  Manual, 
t American  Radiator  Co. 

Combinations  of  the  40,  50,  and  60  indh  sections  may  be  made 
if  large  free  areas  are  required  or  the  length  of  space  is  limited, 
thus,  a  50,  60  combination  of  10  sections  gives  a  free  area  of  16.89 
square  feet. 

To  figure  the  free  area  for  any  job,  flivide  the  total  cubic 
feet  of  air  to  be  furnished  per  minute  by  the  velocity  per  minute, 
which  will  give  the  free  area  in  square  feet. 

307 


TABLE  35. 

Percentage  of  Heat  Transmitted  by  Various  Pipe-Coverings, 

From  Tests  Made  at  Sifoley  College,  Cornell  University, 

and  at  Michigan  University.* 

Relative  Amount 
Kind  of  Covering-.  of  Heat 

Transmitted. 

Naked    pipe 100. 

Two  layers  asbestos  paper,    I   in.   hair  felt,   and  canvas 

cover     15.2 

Two  alyers  asbestos  paper,  1  in.  hair  felt,  canvas  cover, 

wrapped  with   manilla   paper 15 . 

Two  layers  asbestos  paper,   1   in.   hair  felt 17. 

Hair  felt  sectional  covering,  asbestos  lined 18.6 

One  thickness  asbestos  board   59.4 

Four  thicknesses  asbestos  paper 50.3 

Two  layers  asbestos  paper 77.7 

Wool    felt,    asbestos    lined    23.1 

Wool  felt  with  air  spaces,  asbestos  lined 19.7 

Wool   felt,   plaster  paris   lined 25.9 

Asbestos  molded,  mixed  with  plaster  paris 31.8 

Asbestos   felted,   pure   long4   fibre 20.1 

Asbestos  and  sponge    18.8 

Asbestos  and  wool  felt 20.8 

Magnesia,  molded,  applied  in  plastic  condition 22.4 

Magnesia,  sectional   18.8 

Mineral   wool,    sectional    19.3 

Rock  wool,   fibrous    20.3 

Rock  wool,  felted 20.9 

Fossil  meal,  molded,  %  inch  thick 29.7 

Pipe   painted   with   black  asphaltum 105.5 

Pipe  painted  with  light  drab  lead  paint 108.7 

Glossy  white  paint    95.0 

'Carpenter's  H.  ?nd  V.  B. 

Note.— These  tests  agree  remarkably  well  with  a  series 
made  by  Prof.  M.  E.  Cooley  of  Michigan  University,  and  also 
with  some  made  by  G.  M.  Brill,  Syracuse,  N.  Y.,  and  reported 
in  Transactions  of  the  American,  Society  of  Mechanical  En- 
gineers, vol.  XVI. 


308 


TABLE    36. 

Speeds,     Capacities    and    Horse-Powers     of    "A    B     C"    Steel 
Plate  Fans  at  Varying  Pressures. 


a] 

Pressures 

§ 

. 

N 
O 

N 

§ 

s 

8 

N 

H 

O 

§* 

Q£ 

^ 

3* 

O 

iH 

1-1 

i£ 

O 

$ 

CO 

CU.   FT. 

2740 

3900 

4760 

5490 

6090 

6700 

7350 

7750 

8650 

9520 

30 

R.    P.    M. 

S80 

540 

659 

760 

847 

930 

1004 

1075 

1200 

1320 

H.     P. 

0.80 

1.60 

2.66 

3.85 

5.32 

6.65 

8.22 

10.25 

14.38 

18.85 

CU.   FT. 

3550 

5040 

5490 

7100 

7910 

8700 

9410 

10200 

11210 

1233o 

36 

R.    P.    M. 

317 

449 

549 

633 

706 

776 

838 

895 

1000 

1100 

H.     P. 

1.03 

2.05 

3.42 

4.95 

6.84 

8.54 

10.60 

13.2 

18.45 

24.3 

CU.   FT. 

5220 

7350 

9050 

10400 

11600 

12700 

13750 

14750 

16500 

18000 

42 

R.    P.    M. 

271 

383 

471 

542 

605 

663 

716 

768 

857 

938 

H.    P. 

1.51 

3.02 

5.04 

7.30 

10.10 

12.60 

15.60 

19.40 

27.20 

35.7 

CU.   FT. 

6630 

8900 

10940 

12550 

14000 

15350 

16600 

17800 

19890 

21920 

48 

R.    P.    M. 

238 

336 

412 

474 

530 

580 

627 

672 

750 

825 

H.     P. 

1.82 

3.651 

6.06 

8.82 

12.15 

15.20 

18.85 

23.40 

32.80 

43.2 

CU.    FT. 

7850 

11050 

13600 

15600 

17450 

19100 

20650 

22100 

24750 

27300 

54 

R.    P.    M. 

211 

299 

366 

421 

470 

515 

557 

596 

666 

734 

H.     P. 

2.27 

4.53 

7.56 

11.00 

15.10 

18,90 

23.40 

29.10 

40.70 

53.5 

CU.    FT. 

9540 

13500 

16500 

19050 

21300 

23300 

25200 

27000 

30500 

33000 

60 

R.    P.    M. 

190 

268 

329 

380 

424 

464 

502 

537 

600 

659 

H.     P. 

2.76 

5.52 

9.20 

13.35 

18.42 

23.00 

28.60 

35.90 

49.60 

65.2 

CU.   FT. 

11870 

16700 

20600 

23600 

26400 

28900 

31300 

33500 

37500 

41200 

66 

R.    P.    M. 

173 

2441     300 

345 

385 

422 

456 

488 

546 

600 

H.     P. 

3.43 

6.85 

11.44 

16.60 

22.90 

28.60 

35.50 

44.00 

61.7 

81.2 

CU.    FT. 

15000 

21000 

25840 

29700 

33200 

36400 

39400 

42200 

47103 

51800 

72 

R.    P.    M. 

159 

224 

274 

316 

354 

387 

418 

448 

500 

550 

H.     P. 

4.32 

8.56 

14.40 

20.90 

28.80 

36.00 

44.60 

55.45 

77.7 

102.1 

CU.   FT. 

19800 

27900 

34200 

39400 

44000 

48200 

51200 

55800 

63900 

68400 

84 

R.    P.    M. 

136 

192 

235 

271 

302 

331 

357 

383 

439 

470 

H.     P. 

5.72 

11.421 

19.00 

27.60 

38.10 

47.60 

59.00 

73.30 

102.7 

135.5 

CU.   FT. 

25050 

35600 

43700 

50250 

56150 

61500 

66500 

71250 

79200 

87500 

96 

R.    P.    M. 

118 

168 

206 

237 

265 

290 

314 

336' 

373 

412 

H.    P. 

7.29 

14.60 

24.32 

35.20 

48.60 

60.75 

75.30 

93.50 

134.0 

172.0 

CU.   FT. 

31410 

44200 

54300 

62700 

69700 

76700 

82700 

88400 

99000 

108400 

108 

R.    P.    M. 

109 

149 

183 

211 

235 

259 

279 

298 

334 

366 

H.     P. 

9.07 

18.13 

30.24 

43.80 

60.48 

75.5 

93.6 

116.20 

131.  C 

214.0 

CU.   FT. 

38000 

53700 

66000 

75700 

84950 

93000 

100500 

107200 

12CX/X) 

134000 

120 

R.    P.    M. 

95 

134 

165 

189 

212 

232 

251 

268 

300 

330 

PI.     P. 

11.02 

22.20 

36.80 

53.3 

73.5 

92.0 

114.0 

141.5 

198.5 

261.0 

CU.   FT. 

46800 

66300 

80900 

93200 

104000 

113500 

123300 

131400 

^47100 

161500 

132 

R.    P.    M. 

87 

123 

150 

173 

193 

211 

229 

244 

274 

300 

H.     P. 

13.48 

27.00 

44.90 

65.10 

89.6 

112.0 

1J9.0 

173.0 

243.0 

318.0 

CU.   FT. 

56400 

79000 

96500 

12000 

124800 

136800 

147400 

158000 

176100 

194000 

144 

R.    P.    M. 

80 

112 

137 

159 

177 

194 

209 

224 

250 

275 

H.     P. 

16.10 

32.30 

53.80 

78.00 

107.4 

134.0 

166.0 

206.0 

290.0 

382.0 

The  capacities  are  based  on  the  average  results  obtained  when 
applied  to  the  heating  of  buildings,  and  are  reliable  for  such  in- 
stallations. Three  Quarter  ounce  pressure  is  common  practice. 

309 


TABLE    37. 

Speeds,  Capacities  and  Horse-Powers  of  "Green"  Steel  Plate 
Fans    at    Varying    Pressures. 


i| 

Pressures 

§ 

8 

§ 

tsj 
o 

8 

af 

8 

N 
O 

g 

N 
O 

44 

o 

CU.    FT. 

2249 

3176 

3891 

4498 

5029 

5513 

5956 

6372 

7135 

30 

R.    P.    M. 

330 

466- 

571 

660 

738 

809 

874 

985 

1047 

H.     P. 

.286 

.811 

1.491 

2.298 

3.213 

4.227 

5.311 

6.515 

9.120 

CU.    FT. 

3239 

4581 

5605 

6477 

7242 

7937 

8584 

9173 

10268 

36 

R.    P.    M. 

275 

389 

476 

550 

615 

674 

729 

779 

872 

H.     P. 

.413 

1.170 

2.148 

3.311 

4.625 

6.080 

7.681 

9.376 

13.125 

CU.    FT. 

4398 

6214 

7617 

8815 

9864 

10799 

11679 

12483 

13981 

42 

R.    P.    M. 

235 

332 

407 

471 

527 

577 

624 

667 

747 

H.     P. 

.557 

1.576 

2.898 

5.473 

6.300 

8.287 

10.4501 

12.750 

CU.    FT. 

5750 

8123 

9937 

11500 

12867 

14123 

15240 

16301 

18282 

48 

R.    P.    M. 

206 

291 

356 

412 

461 

506 

546 

584 

655 

H.    P. 

.733 

2.076 

3.810 

5.880 

8.223 

10.832 

13.636 

16.670 

23.370 

CU.    FT. 

7602 

10758 

13167 

15203 

17030 

18650 

20145 

21558 

24174 

54 

R.    P,    M. 

183 

259 

sir 

366 

410 

449 

485 

519 

5S2 

H.    P. 

.970 

2.750 

5.047 

7.767 

10.880 

14.300 

18.017 

21.992= 

30.896 

CU.    FT. 

9715 

13718 

16780 

19429 

21725 

23786 

25728 

27495 

307'92 

60 

R.    P.    M. 

165 

233 

285 

330 

369 

404 

437 

467 

523 

H.    P. 

1.241 

3.506 

6.433 

9.932 

13.882 

18.230 

22.996 

28.077 

39.355 

CD.    FT. 

12078 

17071 

20855 

24156 

26975 

29551 

32047 

34221 

38247 

66 

R.    P.    M. 

150 

212 

259 

300 

335 

367 

398 

425 

475 

H.    P. 

1.542 

4.361 

7.996 

12.352 

17.238 

22.666 

28.675 

35.123 

48.895 

CU.    FT. 

15608 

21942 

26918 

31103 

34835 

38115 

41169 

44109 

49312 

72 

R.    P.    M. 

138 

194 

238 

275 

308 

337 

364 

390 

436 

H.    P. 

1.983 

5.601 

10.322 

15.881 

22.252! 

29.223 

36.808 

45.043 

62.783 

CU.    FT. 

20192 

28405 

34907 

40383 

45174 

49452 

53387 

57152 

63996 

84 

R.   P.  M. 

118 

166 

204 

236 

264 

289 

312 

334 

374 

H.    P. 

2.581 

7.262 

13.387 

20.650 

28.875 

37.931 

47.775 

58.450 

81.812 

CU.    FT. 

23008 

32614 

39762: 

46016 

51601 

56515 

60983 

65227 

73045 

96 

R.    P.    M. 

103 

146 

178 

206 

231 

253 

273 

292 

327 

H.    P. 

2.941 

8.337 

15.261 

23.531 

32.982 

43.348 

54.511 

66.707 

93.380 

CU.    FT. 

29260 

41027 

50568 

58519 

65198 

71559 

77284 

82690 

92549 

108 

R.    P.    M. 

92 

129 

159 

184 

205 

225 

243 

260 

291 

H.    P. 

3.737 

10.488 

19.397 

30.060 

41.666 

54.871 

69.163 

84.556 

118.291 

CU.    FT. 

36209 

51043 

62384 

71982 

80270 

88559 

95539 

102083 

114298 

120 

R.    P.    M. 

83 

117 

143 

165 

184 

203 

219 

234 

262 

H.    P. 

4.628 

13.050 

23.925 

36.807 

51.307 

67.928 

85.495 

104.401 

146.116 

CU.    FT. 

43560 

61565 

75504 

87120 

97575 

106868 

115580 

123711 

138231 

132 

R.    P.    M. 

75 

106 

130 

150 

168 

184 

1991 

213 

238 

H.   P. 

5.568 

15.730 

28.957 

44.550 

62.370 

82.096 

103.430 

126.521 

176.715 

CU.    FT. 

52026 

73138 

89726 

103298 

116116 

127426 

137228 

147030 

164378 

144 

R.    P.    M. 

69 

97 

119 

137 

154 

169 

182 

195 

218 

H.    P. 

6.69 

18.700 

34.411 

52.822 

74.221 

97.741 

122.802 

150.371 

210.133 

Note— The  hosre-power  required  to  drive  a  fan  will  vary  ac- 
cording to  the  manner  of  application.  The  horse-powers  given 
above  are  25  per  cent,  greater  than  would  be  required  under  ideal 
conditions. 

310 


TABLE    38. 

Speeds,   Capacities  and  Horse-Powers   of   Sirocco  Type  Fans 
with  No.  1  Blades,  at  Varying  Pressures. 

Figures  given  represent  dynamic  pressures  in  ozs.  per 
square  inch.  For  static  pressure  deduct  28.8%.  For  velocity 
pressure  deduct  71.2%. 


IDiam. 
[Wheel 

Pressures 

8 
g 

8 

^? 

8 
s* 

g 

T-H 

| 

3* 

H 

6 

^ 

N 

O 

^ 

N 

O 

c* 

M 

O 

i 

H 

Q 

n 

CU.   FT. 

155 

220 

2TO 

310 

350 

380 

410 

440 

490 

540 

6 

R.    P.    M. 

1145 

1615 

1980 

2280 

2560 

2800 

3005 

3230 

3616 

3960 

B.    H.    P. 

.0185' 

.052 

.095 

.147 

.205 

.270 

.34 

.42 

.58 

.76 

CU.   FT. 

350 

500 

610 

700 

790 

860 

930 

1000 

1110 

1220 

9 

R.    P.    M. 

762 

1076 

1320 

1524 

1700 

1866 

2020 

31521 

2408 

2040 

B.    H.    P. 

.042 

.118 

.216 

.333 

.463- 

.610 

.77 

.95 

1.3* 

1.73 

CU.    FT. 

625 

880 

1080 

1250 

1400 

1530 

1650 

1770 

1970 

2170 

12 

R.    P.    M. 

572 

808 

990 

1145 

1280 

1400 

1512 

1615 

1808 

1980 

B.    H.    P. 

.074 

.208 

.381 

.588 

.80 

1.08 

1.36 

1.60     2.32 

3.05 

CU.    FT. 

975 

1380 

1690 

1950 

2180 

2400 

2590 

2760     3090 

3390 

15 

R.    P.    M. 

456 

645 

790 

912 

1020 

1120 

1210 

1290,     1444 

1580 

B.    H.    P. 

.115 

.326 

.600 

.923 

1.29 

1.69 

2.14 

2.61     3.65 

4.8 

CU.    FT. 

1410 

1990 

2440 

2820 

3160 

3450 

3720 

3980     4450 

4830 

18 

R.    P.    M. 

381 

538 

660 

762 

850 

933 

1010 

1076|     1204 

1320 

B.    H.    P. 

.167 

.470 

.862 

1.33 

1.85 

2.43 

3.07 

3.75 

5.25 

6.9 

CU.   FT. 

1925 

2710 

3310 

3850 

4290 

4700 

5070 

5420 

6060 

6620 

21 

R.    P.    M. 

326 

463 

565 

652 

730 

800 

864 

924 

1032 

1130 

B.    H.    P. 

.227 

640 

1.17 

1.81 

2.53 

3.33 

4.18 

5.11 

7.15 

9.  A 

CU  .    FT  . 

2500 

3540 

4340 

5000 

5600 

6120 

6620 

7080 

7900 

8680 

24 

R.     P.    M.     286 

404 

495 

572 

640 

700 

756 

807 

904 

990 

B.    H.    P. 

.296 

.832 

1.53 

2.35 

3.28 

4.32 

5.44' 

6.64 

9.3 

]2.2 

CU.    FT. 

3175 

4490 

5500 

6350 

7100 

7780 

8400 

8980 

10050 

11000 

27 

R.    P.    M. 

254 

359 

440 

508 

568 

622 

673 

718 

804 

88Q 

B.    H.    P. 

.373 

1.05 

1.94 

2.98 

4.16 

5.48 

6.90 

8.44 

11.8 

15.fi 

CU.   FT. 

3910 

5520 

6770 

7820 

8750 

9600 

10350 

11050 

12330 

13550 

30 

R.    P.    M. 

228 

322 

395 

456 

510 

560" 

604 

645 

723 

790 

B.    H.    P. 

.460 

1.30 

2.40 

3.68 

5.15 

6.75 

8.53 

10.4 

14.5 

19.1 

CU    FT. 

5650 

7950 

9750 

11300 

12640 

13800 

14900 

15900 

178CO 

19500 

36 

R.    P.    M. 

190 

269 

330 

381 

425 

466 

504, 

538 

602 

660 

B.    H.    P. 

.665 

1.87 

3.44 

5.30 

7.40 

9.72 

12.29 

15.0 

20.9 

27.5 

CU  .    FT  . 

770 

10850 

13300 

15400 

17170 

18800 

20300 

21700 

24250 

26600 

42 

R.    P.    M. 

163 

231 

283 

326 

365 

400 

432 

463 

516 

566 

B.    H.    P. 

.903 

2.55 

4.69 

7.24 

10.1 

13.3 

16.7 

20.4 

28.5 

87.5 

311 


II 

£Q 

Pressures 

§ 

§ 

i 

o 

M 

N 

O 

S* 

N 

O 

N 
O 

g 

o 

N 
O 

ot 

5 

CU.   FT. 

10000 

14150 

17350 

20000 

22400 

24500 

26500 

28300 

31600 

34700 

48 

R.    P.    M. 

143 

202 

248 

286 

320 

350 

378 

403 

452 

495 

B.    H.    P. 

1.18 

3.32 

6.10 

9.40 

13.1 

17.2 

21.75 

26.0 

37.1 

48.8 

CU.    FT. 

12700 

17950 

22000 

25400 

28400 

31100 

33600 

35900 

40200 

44000 

54 

R.    P.    M. 

127 

179 

220 

254 

284 

311 

336 

359 

4025 

440 

B.    H.    P. 

1.49 

4.20 

7.75 

11.9 

16.6 

21.9 

27.6 

,33.7 

47.1 

62 

CU.   FT. 

15650 

22100 

27100 

31300 

35000 

38400 

41400 

44200 

49400 

54200 

60 

R.    P.    M. 

114 

161 

198 

228 

255 

280 

302 

322 

sen. 

396 

B.    H.    P 

1.84 

5.20 

9.58 

14.7 

20.6 

27.0 

34.1 

41.6 

58.2 

76.5 

CU.   FT. 

18950 

26800 

32850 

37900 

42300 

46400 

50100 

53600 

60000 

65700 

66 

R.    P.    M. 

104 

147 

180 

208 

232 

254 

275 

294 

328' 

360 

B.    H.    P. 

2.23 

6.30 

11.6 

17.8 

24.9 

32.7 

41.2 

50.4 

70.4 

92.6 

CU.   FT. 

22600 

31800 

39000 

45200 

50600 

55200 

59600 

63600 

71200 

78000 

72 

R.    P.    M. 

95 

134 

165 

190 

212 

233 

253 

269 

301 

330 

B.    H.    P. 

2.66 

7.48 

13.7 

21.2 

29.6 

38.9 

49.0 

59.8 

83.6 

no 

CU.   FT. 

26400 

37350 

15800 

52800 

59100 

64700 

70000 

74700 

83500 

91600 

78 

R.    P.    M. 

88 

124 

15S 

176 

197 

215 

2331 

248 

278 

305 

B.    H.    P. 

3.10 

8.77 

16.1 

24.8 

34.7 

45.6 

57.5 

70.2 

98 

129 

CU.    FT. 

40800 

i3400 

1.3200 

61600 

38700 

75200 

812CO 

86800 

97100 

L06400 

84! 

R.    P.    M. 

81 

115 

142 

163 

182 

200 

216 

231 

258 

283 

B.    H.    P. 

3.61 

10.2 

18.7 

28.9 

40.4 

63.0 

66.8 

81.7 

114 

150 

CU.   FT. 

452St 

i9800 

61000 

70500 

/8800 

86400 

93300 

99600 

111200 

122000 

90 

R.    P.    M. 

7t 

107 

133 

152 

170 

186 

201 

214 

241 

264 

B.    H.    P. 

4.14 

11.7 

21.5 

33.1 

46.2 

60.7 

76.7 

93.6 

131 

172 

312 


TABLE  39. 
Dimensions  of  Ells  and  Tees  for  Wrought  Iron  Pipe. 


SIZE 


E 


1- 


4- 

4-1/, 

5- 

6- 


6-34 


l-t's 

TT/ 


1- 

l-jl 


4- 


2-J4 

2-% 
S-% 
4- 


6- 

6-% 


i- 
i- 

i-ys 


2- 
2-% 


4- 

4-% 


Diagrams  for  Pipe  Sizes  and  Friction  Heads. 

To  illustrate  the  use  of  the  two  following  diagrams,  ap- 
ply to  the  pipe  line  B,  C,  Art.  144.  First,  let  I  =  1500  feet, 
d  =  8  inches  and  v  =  5  feet  per  second.  Trace  along  the 
velocity  line  until  it  intersects  the  diameter  line,  then  fol- 
low the  ordinate  to  the  top  of  the  page  and  find  the  friction 
head,  13  feet  for  1000  foot  run  or  19.5  feet  for  the  1500  foot 
run.  Second,  let  Q  =  1.75  cubic  feet  per  second  and  d  =  8 
inches.  Trace  to  the  left  along  the  horizontal  line  represent- 
ing the  volume  of  1.75  cubic  feet  until  it  intersects  the 
diameter  line,  then  read  up  and  find  the  same  friction  head 
as  before.  Third,  let  the  allowable  iriction  head  for  1500 
feet  of  main  be  19  feet,  when  Q  =  1.75  cubic  feet  per  second 
or  when  v  =  5  feet  per  second.  Reverse  the  process  given 
above  and  find  an  8  inch  pipe. 


313 


as:  ex-  J-.: 

•5   rv 


£     O 

5-3* 


«-  .=  £=  £  o        v      ;  \x         ".        u 

i*S^3s:id^     \      ,- 
«5i>:rsoLtv  %     '  .> 


314 


315 


INDEX 


Absolute  pressure,  11 

temperature,  10 

Advantages  of  vac.  systems,  169 
Air,  amount  to  burn  carbon,  32 
circulation,  furnace  system,  47 
circulation  within  room,  69 
composition,  14 
exhausted  from   nozzle.  152 
horse  power  in  moving,  154 
humidity  of,  23 
leakage,  heat  loss  by,  37 
needed,  plenum  system,  136 
per  person,  table  of,  21 
required   as   heat  carrier,   48 
temperatures,  plenum  system,  142 
valves,  91 

velocity,  plenum  system,  136,  148 
ventilating,  per  person,  19 
washing  and  humidifying,  131 
Anchors,  types  of,  192 
Anemometer,  29 
Appendix 

table    1    squares,  cubes,  etc.,  271 
table    2    properties  of  steam,  278 
table    3   Naperian  logarithms,  285 
table    4   water    conversion    fac- 
tors, 285 
table    5   volume   and   weight   of 

dry  air,  286 

table    6   weight  of  pure  water,  287 
table    7   boiling   points   of   water, 

289 
table    8   weight   of   water   in    air, 

289 

table    9   properties    of    air,    290 
table  10   relative  humidities,   291 
table  11    fuel  values  Am.  coal,  292 
table  12   cap.  of  chimneys,  293 
table  13   equalization  of  smoke 

flues,  294 

table  14-  diam.    of   registers,    294 
table  15   specific  heat,  etc.,  of  sub- 
stances, 295 
tables  16,  18  capacities  of  furnaces, 

296,   297 
table  17   capacities    of    pipes    and 

registers,  296 

table  19    area  vertical  flues,  297 
tables  20,  21  water  pressures,  298 
table  22   wrought  iron  pipes,  299 
table  23   expansion  of  pipes,  300 
table  24   tapping  list  of  rad.,  300 
table  25   pipe   equalization,   301 
table  26   cap.  hot  water  risers,  302 
table  27   cap.  steam  pipes,  302 
table  28    cap.  hot  water  pipes,  303 
table  29  cap.  hot  water  mains,  303 


tables  30,  31  sizes  of  steam  mains, 

304,  305 
table  32  loss   of  head   by   friction 

of  pipes,  306 

table  33  expansion   tanks,    307 
table  34  sizes  of  Vento  heaters,  307 
table  35  heat   trans,   through  pipe 

coverings,  308 

tables  36,  37,  38  speeds,  cap.  h.  p. 
of  various  fans,  309-312 
table  39  dim.    ells    and   tees,   313 
Application  of  plenum  system,  162 
Area  of  ducts,  plenum  system,  136 
Arrangement  of  Vento  heaters,  145 

of  coils,  plenum  system,  144 
Automatic  vacuum  sys.,  piping,  177 
Automatic  valves,  177 

Basement  plans,  plenum  sys.,  165 

Belvac  thermofiers,   175 

Blowers  and  fans,  119 
speeds  of,  table,  158 
work,  Carpenter's  rules,  155 

Boilers,  223 
feed  pumps,  221 
capacity  and  number  of,  227 
radiation  supplied  by,  224 

Boiling  point  of  water,  table,  289 

British  thermal  unit,  8 
lost  in  plenum  system,  140 

Building  material  conductivities,  36 

Calculating  chimney  area,  32 
Calculating  heat  losses,  35 
Calorie,  8 

Carbon,  amount  of  air  to  burn,  32 
Carbon  dioxide,  per  cent,  table,  19 
Carbon  dioxide,  tests  for,  16 
Carpenter's  practical  rules,  155 
Cast  radiators,  82,  84 
Cast  surfaces,  plenum  systems,  126 
Centrifugal  pumps,  219 
Chart,  hygrometric,  26 
Chimneys,  33 

capacity  of,  table,  293 
Circulating  duct  in  furnace  design, 

65 

Circulating  pumps,  216 
Circulating  water  to  condense 

steam,  209 

Classification  of  radiators,  82 
Coal,  fuel  values  of.  table,  292 
Coil  surface,  plenum  system,  124, 

125,  129,  141 
Combination  heaters,  63 

system,  87 
Condensation,  dripping  from  mains, 


318 


INDEX 


return  to  boilers,  110 
Condenser  for  exhaust  steam,  210 

heating  surface  in,  211 
Conduction,  12 

Conductivities    of    building    materi- 
als, 86 

Conduits,  central  station  htg.,  185 
Convection,  13 

Conversion  factors  for  water,  285 
Data  table  for  plenum  systems,  164 
Design,  hot  water  and  steam,  93 

reports,    instructions    for   1,    2,    3, 
258 

reports,  instructions  for  4,  259 

reports,  instructions  for  5,  261 

Determination  of  pipe  sizes,  99 
Direct  radiation,  tapping  list,  table, 

300 

Dirt  strainer,  Webster,  173 
District  heating,  181 

adaptation  to  private  plants,  239 

amount  of  radiation  supplied,  208 

amount  supplied  by  reheater,  213 

application  to  typical  design,  239 

boiler  feed  pumps,  221 

by  steam,  236 

condensation  from  mains,  239 

conduits,  185 

cost  of  heating,  230 

cost,  summary  of  tests  232 

diameter  of  mains,   205 

economizers,  225 

exhaust  steam  used  in,  194,  210 

future  increase,  202 

heating   surface    in    reheater,   211, 
213 

high  pressure  steam  heater,  216 

important  reheater  details,  214 

layout  for  conduit  mains,  188 

power  plant  layout,  231 

pressure  drop   in  mains,   203,   205, 
237 

radiation  in  district.  202 

radiation  supplied  by  1  h.   p.   of 
ex.  St.,  209 

regulation,  235 

scope  of  work,  183 

service  connections,  207 

steam  available  for  heating,  207 

systems  classified,  182,  200 

typical  design,  193 

velocity  of  water  in  mains,  205 
Division  of  coils,  plenum  sys.,  129 
Ducts,  furnace,  cold  air,  53 

plenum  system,  129,  130 

recirculating,  65 

Economizers,  225 

radiation  supplied  by,  225 

surface,   226,  227 

Efficiency  of  plenum  coils,  table,  139 
Electrical  heating,  253 

formulas  used  in,  253 


Exhaust  stepm  available  in  district 

plants,  194-199 

Exhaust  steam  condenser,  210 
Expansion  joints,  190 

tanks,  92 
Exposure  heat  losses,  table,  38 

Factor  table,  velocity  and  vol.,  152 
Fans  and  blowers..  70,  119 

drives,  157 

housings,  121 

power  of  engine  for,  159 
Fire  places,   stoves,  etc.,  117 
Fittings,  steam  and  hot  water,  89 
Floor  plans   for  furnace  heating, 

106-108 

Floor  plans  for  plenum  sys.,  165-167 
Formulas,  empirical  for  radiation,  96 
Fresh  air  duct,  53-64 
Fresh  air  entrance  to  bldgs.,  123 
Fuel  values  of  Am.  coals,  table,  292 
Furnace, 

air  circulation  within  room,  69 

foundations,  64 

heating,  45 

location,  64 

selection,  60 
Furnace  system,  air  circulation,  47 

air  required  as  heat  carrier,  47 

circulating  duct  in,  65 

design  of,  55 

essentials  of,  46 

fan  in,  70 

fresh  air  duct  in,  53,  64 

grate  area  in,  63 

gross   register   area   in,   51 

heat  stacks,  sizes  of,  51,  67 

heating  surface  in,  54 

leader  pipes  in,  52,  66 

net  vent  register  in,  51 

plans  for,  57 

points  to  be  calculated  in,  47 

registers,  temperatures  in,  50 

stacks  or  risers  in,  67 

three  methods  of  installation,  49 

vent  stacks,  69 

Gage  pressures,  11 

Grate  area,  boilers  and  heaters,  101 
Grate   area   for   furnaces,   53 
Greenhouse  heating,  97 

Hammer,  water,  110 
Heat   given   off  by  persons,   lights, 
etc.,  43 

latent,  11 

measurement  of,  8 

mechanical  equivalent   of,  11 

stacks,  sizes  of,  51,  67 
Heaters,  hot  water,  87 
Heating,  district,  cost  of,  230 
Heating  surface  in  coils,  plenum  sys- 
tem, 137 


INDEX 


319 


Heating  sur.,  in  economizer,  226,  227 

in  furnace  system,  54 

in  reheater,  211 

per  h.  p.  in  reheater,  213 
Heat  loss,  37,  38,  39,  41,  134 

calculation  of,  35 

combined,  41 

for  a  10  room  house,  table,  56 
High  pressure  heater,  216 
High  pressure  steam  trap,  110 
Horse  power,  in  moving  air,  154,  155 

of  engine  for  fan,  159 

required   to   move    air    in   plenum 

system,  150 
Hot  air  pipes,  cap.  of,  table,  296 

water  heaters,  87 

water  pipes,  capacity  of,  table,  302 

water  radiators,  85 

water  risers,  cap.  of,  table,  303 

water  system,  72 

water  used  in  indirect  coils  in  ple- 
num, system,  146 
Hot  water  and  steam  heating, 

calculations  for  rad.  sur.  for,  93 

classifications,  75 

determination  of  pipe  sizes  for,  99 

empirical  formula  for,  96 

grate  area  for  heater,  101 

greenhouse  radiation,  97 

location  of  radiators  for,  102 

parts  of,  73 

pitch  of  mains  for,  102 

principles  of  design  of,  93 

second   classification  of,   76 

typical  layout  of,  103 
Humidity  of  the  air,  23 
Humidities,  relative,  table,  291 
Hygrodeik,  24 
Hygrometer,  23 
Hygrometric  chart,  26 

Indirect  radiators,  76 
Installation  of  steam  pipes,  109 
Instructions  for  design  reports,  Nos. 

1,  2,  3,  258 

for  design  report,  No.  4,  259 
for  design  report,  No.  5,  261 
'K,'  values  for  pipe  coils,  table,  139 
'K,'  values  for  Vcnto  coils,  table, 

141 

outline  of  course  in,  257 
suggestions  for  course  in,  256 

Latent  heat,  11 

Layout  for  furnace  system,  106 

for  hot  water  heating  plant,  103 

for  plenum  system,  127,  128 

of  power  plant,  231 

steam  mains  and  conduits,  188 
Leader  pipes,  52,  66 
Location  of  furnaces,  64 

of  radiators,  102 
Low  pressure  steam  traps,  110 


Mains,  condensation,  dripping  from, 
239 

cap.  of  hot  water,  table,  303 

diameter  of,  205 

pitch  of,  102 

pressure  drop  and  diameter  of,  237 

velocity  of  water  in,  205 
Manholes,  193 
Measurement  o,f  air  velocities,  29 

of  heat,  8 

of  high  temperatures,  9 
Mechanical  vacuum  steam  htg.  sys., 

advantages  of,  169 

automatic  pump  for,  172 

Automatic  system,  177 

Paul  system,  177 

principal  features  of,  170 

Van  Auken,  175 

Webster  system,  173 
Mechanical  equivalent  of  heat,  11 
Mechanical    warm    air    heating    and 
ventilating  sys.,  117,  133,  148 

blowers  and  fans  for,  119 

definitions  of  terms,  133 

elements  of,  117 

exhaust,  118 

heat  loss  and  cu.  ft.  air  exhausted, 
134 

theoretical  considerations  for,  133 

variations  in  design  of,  118 
Mills  system  (attic  main),  78 
Modulation  valve  for  Webster  Bys- 

tem,  175 
Moisture,  addition  of,  to  air,  27 

with  air,  22 

Naperian  logarithms,  table,  285 
Nitrogen,  15 
'n,'  values  of,  41 

Operation  of  hot  water  heaters  and 
boilers, 

of  furnaces,  70 

suggestions  for.  114 
Oxygen,  15 

Paul  sys.  of  mech.  vac.  heating,  177 
typical  piping  connections  for,  178 

Pipe  coil  radiators.  83 
capacity   of,   in   sa.   ft.   of  steam 

radiation,  302 
equalization,  table  of,  301 
sizes,  determination  of,  99 

Pipe,  leader,  52,  66 

Piping     connection     around    heater 

and  engine,  161 

connections  for  auto.  vac.  sys.,  177 
connections  for  Paul  sys.,  178 
for  heatg.  sys.  definitions,  74 
system  for  automatic  control  of, 
Webster  system,  175 

Pitot  tubes,  30 

Plans  and  sped,  for  htg.  sys.,  263 
typical  specifications,  264 


318 


INDEX 


return  to  boilers,  110 
Condenser  for  exhaust  steam,  210 

heating  surface  in,  211 
Conduction,  12 

Conductivities    of    building    materi- 
als, 86 

Conduits,  central  station  htg.,  185 
Convection,  13 

Conversion  factors  for  water,  285 
Data  table  for  Dlenum  systems,  164 
Design,  hot  water  and  steam,  93 

reports,    instructions    for   1,    2,    3, 
258 

reports,  instructions  for  4,  259 

reports,  instructions  for  5,  261 

Determination  of  pipe  sizes,  99 
Direct  radiation,  tapping  list,  table, 

300 

Dirt  strainer,  Webster,  173 
District  heating,  181 

adaptation  to  private  plants,  239 

amount  of  radiation  supplied,  208 

amount  supplied  by  reheater,  213 

application  to  typical  design,  239 

boiler  feed  pumps,  221 

by  steam,  236 

condensation  from  mains,  239 

conduits,  185 

cost  of  heating,  230 

cost,  summary  of  tests  232 

diameter  of  mains,   205 

economizers,  225 

exhaust  steam  used  in,  194,  210 

future  increase,  202 

heating   surface    in    reheater,    211, 
213 

high  pressure  steam  heater,  216 

important  reheater  details,  214 

layout  for  conduit  mains,  188 

power  plant  layout,  231 

pressure   drop   in   mains,   203,   205, 
237 

radiation  in  district,  202 

radiation  supplied  by  1  h.   p.   of 
ex.  st.,  209 

regulation,  235 

scope  of  work,  183 

service  connections,  207 

steam  available  for  heating,  207 

systems  classified,  182,  200 

typical  design,  193 

velocity  of  water  in  mains,  205 
Division  of  coils,  plenum  sys.,  129 
Ducts,  furnace,  cold  air,  53 

plenum  system,  129,  130 

recirculating,  65 

Economizers,  225 

radiation  supplied  by,  225 

surface,   226,  227 

Efficiency  of  plenum  coils,  table,  139 
Electrical  heating,  253 

formulas  used  in,  253 


Exhaust  steam  available  in  district 

plants,  194-199 

Exhaust  steam  condenser,  210 
Expansion  joints,  190 

tanks,  92 
Exposure  heat  losses,  table,  38 

Factor  table,  velocity  and  vol.,  152 
Fans  and  blowers..  70,  119 

drives,  157 

housings,  121 

power  of  engine  for,  159 
Fire  places,   stoves,   etc.,   117 
Fittings,  steam  and  hot  water,  89 
Floor  plans   for  furnace  heating, 

106-108 

Floor  plans  for  plenum  sys.,  165-167 
Formulas,  empirical  for  radiation,  96 
Fresh  air  duct,  53-64 
Fresh  air  entrance  to  bldgs.,  123 
Fuel  values  of  Am.  coals,  table,  292 
Furnace, 

air  circulation  within  room,  69 

foundations,  64 

heating,  45 

location,  64 

selection,  60 
Furnace  system,  air  circulation,  47 

air  required  as  heat  carrier,  47 

circulating  duct  in,  65 

design  of,  55 

essentials  of,  46 

fan  in,  70 

fresh  air  duct  in,  53,  64 

grate  area  in,  63 

gross   register   area   in,   51 

heat  stacks,  sizes  of,  51,  67 

heating  surface  in,  54 

leader  pipes  in,  52,  66 

net  vent  register  in,  51 

plans  for,  57 

points  to  be  calculated  in,  47 

registers,  temperatures  in,  50 

stacks  or  risers  in,  67 

three  methods  of  installation,  49 

vent  stacks,  69 

Gage  pressures,  11 

Grate  area,  boilers  and  heaters,  101 
Grate   area   for   furnaces.   53 
Greenhouse  heating,  97 

Hammer,  water,  110 
Heat   given  off  by  persons,   lights, 
etc.,  43 

latent,  11 

measurement  of.,  8 

mechanical  equivalent   of,  11 

stacks,  sizes  of,  51,  67 
Heaters,  hot  water,  87 
Heating,  district,  cost  of,  230 
Heating  surface  in  coils,  plenum  sys- 
tem, 137 


INDEX 


Heating  sur.,  in  economizer,  226,  227 

in  furnace  system,  54 

in  reheater,  211 

per  h.  p.  in  reheater,  213 
Heat  loss,  37,  38,  39,  41,  134 

calculation  of,  35 

combined,  41 

for  a  10  room  house,  table,  56 
High  pressure  heater,  216 
High  pressure  steam  trap,  110 
Horse  power,  in  moving  air,  154,  155 

of  engine  for  fan,  159 

required   to   move    air    in   plenum 

system,  150 
Hot  air  pipes,  cap.  of,  table,  296 

water  heaters,  87 

water  pipes,  capacity  of,  table,  302 

water  radiators,  85 

water  risers,  cap.  of,  table,  303 

water  system,  72 

water  used  in  indirect  coils  in  ple- 
num system,  146 
Hot  water  and  steam  heating, 

calculations  for  rad.  sur.  for,  93 

classifications,  75 

determination  of  pipe  sizes  for,  99 

empirical  formula  for,  96 

grate  area  for  heater,  101 

greenhouse  radiation,  97 

location  of  radiators  for,  102 

parts  of,  73 

pitch  of  mains  for,  102 

principles  of  design  of,  93 

second   classification   of,   76 

typical  layout  of,  103 
Humidity  of  the  air,  23 
Humidities,  relative,  table,  291 
Hygrodeik,  24 
Hygrometer,  23 
Hygrometric  chart,  26 

Indirect  radiators,  76 
Installation  of  steam  pipes,  109 
Instructions  for  design  reports,  Nos. 

1,  2,  3,  258 

for  design  report,  No.  4,  259 
for  design  report,  No.  5,  261 
'K,'  values  for  pipe  coils,  table,  139 
'K,'  values  for  Vcnto  coils,  table, 

141 

outline  of  course  in,  257 
suggestions  for  course  in,  256 

Latent  heat,  11 

Layout  for  furnace  system,  106 

for  hot  water  heating  plant,  103 

for  plenum  system,  127,  128 

of  power  plant,  231 

steam  mains  and  conduits,  188 
Leader  pipes,  52,  66 
Location  of  furnaces.  64 

of  radiators.  102 
Low  pressure  steam  traps,  110 


Mains,  condensation,  dripping  from, 
239 

cap.  of  hot  water,  table,  303 

diameter  of,  205 

pitch  of,  102 

pressure  drop  and  diameter  of,  237 

velocity  of  water  in.  205 
Manholes,  193 
Measurement  of  air  velocities.  29 

of  heat.  8 

of  high  temperatures,  9 
Mechanical  vacuum  steam  htg.  sys., 

advantages  of.  169 

automatic  pump  for,  172 

Automatic  system,  177 

Paul  system,  177 

principal  features  of,  170 

Van  Auken,  175 

Webster  system,  173 
Mechanical  equivalent  of  heat,  11 
Mechanical   warm    air   heating    and 
ventilating  sys.,  117,  133,  148 

blowers  and  fans  for,  119 

definitions  of  terms,  133 

elements  of,  117 

exhaust,  118 

heat  loss  and  cu.  ft.  air  exhausted, 
134 

theoretical  considerations  for,  133 

variations  in  design  of,  118 
Mills  system  (attic  main),  78 
Modulation  valve  for  Webster  sys- 
tem, 175 
Moisture,  addition  of,  to  air,  27 

with  air.  22 

Naperian  logarithms,  table,  285 
Nitrogen,  15 
'n,'  values  of,  41 

Operation  of  hot  water  heaters  and 
boilers, 

of  furnaces,  70 

suggestions  for.  114 
Oxygen,  15 

Paul  sys.  of  mech.  vac.  heating,  177 
typical  piping  connections  for,  178 

Pipe  coil  radiators.  83 
capacity   of,   in  sa.   ft.   of  steam 

radiation,  302 
equalization,  table  of.  301 
sizes,  determination  of,  99 

Pipe,  leader,  52,  66 

Piping     connection     around    heater 

and  engine,  161 

connections  for  auto.  vae.  sys.,  177 
connections  for  Paul  sys.,  178 
for  heatg.  sys.  definitions,  74 
system  for  automatic  control  of, 
Webster  system,  175 

Pitot   tubes,   30 

Plans  and  speci.  for  htg.  sys.,  263 
typical  specifications,  264 


320 


INDEX 


Plenum   system,   actual    amount   of 
air  exhausted  in,  152 

air  needed  cu.  ft.  per  hour  in,  136 

air  velocity,  table,  136 

air  velocity  theoretical  in,  148 

air  washing  and  humidifying,  131 

amount  of  steam  condensed,  146 

application  of  to  school  bldgs.,  162 

approximate  rules  for,  142 

approximate  sizes  of   fan  wheels, 
table,  156 

arrangement  of  coils  in  pioe  heat- 
ers, 144 

arrangement  of  sees,  and  stacks  in 
Vento  heaters,  145 

basement  plans  for,  165 

blower  fans  actual  h.  D.  to  move 
air,  155 

Carpenter's  rules  for,  155 

cast  surface  for,  126 

coil  surface  in,  124,  125 

cross   sectional   area   ducts,   regis- 
ters, etc.,  136 

data,  table,  164 

division  of  coil  surface  in,  129 

double  ducts  in,  130 

dry  steam  needed  in  excess  of  exh. 
from  engine,  147 

efficiency  and  air  temp.,  table  139 

factors  for  change  of  velocity  and 
volume,  table,  152 

fan  drives  for,  157 

final  air  temperature  in,  142 

floor  plans  for,  165-167 

heating  surface  in  coils  of,  137 

heating  surfaces,  124 

h.  p.  of  engine  for  fan  for,  159 

h.  p.  to  move  air,  table,  150 

'K,'  values  of,  138 

layout,  127,  128 

piping  connections   around  heater 
and  engine,  161 

pressure   and   velocity,   results   of 
tests  of,  153 

single  duct  in,  129 

speed  of  blower  fans,  table,  158 

speed  of  fans  for,  157 

temp,  of  air  at  register  in,  135 

temp,  of  air  leaving  coils,  143 

total  B.  t.  u.  transmitted  per  hr., 
table,  140 

use  of  hot  water  in  indirect  coils, 
146 

values  of  'K,'  138 

velocity  of  air  escaping  to  atmos- 
phere, table,  151 

work  done  in  moving  air,  154 
Power  plant  layout,  231 
Pressed  steel  radiators,  84 
Pressure,  absolute,  11 

and    velocity,   results    of  tests,  153 

gage,  11 

in  ounces  per  SQ.  in.,  table,  298 

water  in  mains,  203 


Principal  features  of  mechanical  vac- 
uum heating  system,  170 
Properties  of  air,  290 
Properties  of  steam,  table,  278 
Pumps,  boiler  feed,  221 

centrifugal,  219 

circulating,  216 

city  water  supply,  221 

for  mech.  vac.  steam  heating,  172 


Radiation,  12 

amount    of    one   sa.    ft.    reheater 
tube  surface  will  supply,  213 

amt.  supplied  by  economizer,  225 

amt.  supplied  by  one  h.  p.,  224 

hot  water,  85 

one  Ib.  exh.  steam  will  supply,  208 

supplied  by  1  h.  p.  exh.  steam,  209 

sur.  to  heat  circulating  water,  226 

surface  to  heat   feed  water,  227 
Radiators,  amt.  of  surface  on,  86 

cast,  83,  84 

classification  of,  82 

columns  of,  83 

direct,  75 

direct-indirect,  75 

height  of,  85 

indirect,  76 

location  and  connection  of,  102 

pipe  coil,  83 

pressed  steel,  84 

sizes,    etc.,    for   ten   room    house, 
table,  105 

sizes,  table  of,  86 

steam,  85 

surface  calculation  for,  93 

sur.  effect  on  trans,  of  heat,  86 
Recirculating  duct,  65 
Register,  area  of.  51 

diameter  of.  table,  294 

ducts,  area  of,  136 

sizes,  net  heat,  50 

temperature,  50 
Regulation,  district  heating,  235 

Sylph  on  damper,  245 
Room  temperature,  standard,  42 

Service  connections,  207 

Single  duct,  plenum  system,  129 

Sizes    of    fan    wheels,    approximate, 

table,  156 

Smoke  flues,  equalization  of,  294 
Specifications  for  plans,  257,  264 
Specific  heat,  12 

heats,  etc.,  of  substances,  295 
Speeds  of  blower  fans,  157,  158 
Squares,  cubes,  etc.,  table,  271 
Stacks  and  risers.  67 
Standard   room  temperature,   42 
Steam  and  hot  water  fittings,  89 

available   for   heating   circulating 
water,  207 

boilers,  87 


INDEX 


condensed  per  SQ.   ft.   of   heating 

sur.  per  hour,  plenum  sys.,  146 
dryf    needed    in    excess    of    engine 

exhaust,  147 

heater,  high  pressure,  216 
heating,  district,  236 
pipe  installation,  109 
radiators,  85 
traps,  high  pressure,  110 
Steam  system,  72 

amt.  condensed  in  plenum  sys.,  146 
classification,  75 
parts  of,  73 

second  classification  of,  76 
Street  mains   and  conduits,  layout, 

188 
Suggestions  for  operating  hot  water 

heaters  and  boilers,  114 
for  operating  furnaces,  70 
Sylphon  damper  regulator,  245 

Table  I    determination  of  COa,  19 
Tables  II,  III  volume  of  air  per  per- 
son, 21 
Table  IV  conductivities  of  materials, 

36 

Table  V  exposure  losses.  38 
Table  VI  values  of  t1,  42 
Table  VII  values  of  t=> ,  43 
Table  VIII  heat  given  off  by  per- 
sons, lights,  etc.,  43 
Table   IX   application,   to  10  room 

res.,  56 

Table  X  size  and  sur.  of  rads.,  86 
Table  XI  temi>.  of  water  in  mains, 

99 

Table  XII  summary,  h.  w.  htg.,  105 
Table  XIII  vel.  in  plenum  sys.,  136 
Tables  XIV-XVII  efficiencies  of  coils, 

139-141 
Tables  XVIII-XIX  temp,   of  air  on 

leaving  coils,  143 
Tables    XX-XXII    air    pressure    and 

velocity,  150-152 
Table  XXIII  sizes  of  fans.  156 
Table  XXIV  speeds  of  fans,  158 
Table  XXV  data  for  plenum  sys.,  164 
Table  XXVII   pressure  of  water  in 

mains,  205 

Table  XXVIII  cal.  of  conduit  mains, 
241 


Table 
Table 
Table 
Table 


Table  5 
Table  6 
Table  7 
Table  8 
Table  9 
Table  10 
Table  11 


squares,  cubes,  etc.,  271 
properties  of  steam,  278 
Naperian  logarithms,  285 
water  conversion  factors, 

285 

vol.  and  wt.  of  dry  air,  286 
weight  of  pure  water,  287 
boiling  points  of  water,  289 
weight  of  water  and  air,  289 
properties  of  air,  290 
relative  humidities,  291 
fuel  values  of  Am.  coal,  292 


Table  12  capacities  of  chimneys,  293 
Table  13  equalization  of  smoke  flues, 

294 

Table  14  diameter  of  registers,  294 
Table  15  sp.  ht.,  etc.,  of  substances, 

295 

Tables  16,  18  cap.  of  fur.,  296,  297 
Table  17  cap.  of  pipes  and  reg.,  296 
Table  19  area  vertical  flues,  297 
Table  20,  21  water  pressures,  298 
Table  22  wrought  iron  pipes,  209 
Table  23  expansion  of  pipes,  300 
Table  24    tapping  list  of  rad.,  300 
Table  25    pipe  equalization,  301 
Table  26  capacities1  of  hot  water 

risers,  302 

Table  27  cap.  of  steam  pipes,  302 
Table  28  cap.  of  hot  water  pipes,  303 
Table  29  cap.  of  hot  water  mains,  303 
Tables  30   31  sizes  of  steam  mains. 

304      305 
Table  32  loss  of  head  by  friction  ol 

pipes,  306 

Table  33  expansion  tanks,   307 
Table  34  sizes  of  Vento  heaters,  307 
Table  35  heat    trans,    through    pipe 

coverings,    308 

Tables  36,  37,  38  speeds,  cap.  h.  p.  of 
various'    fans,    309-312 
Table  39  dim.  of  ells  and  tees,  313 
Tanks,  expansion,  92 
Temperature  absolute,  10 

measurement  of  high,  9 

of  air  entering  plenum  system,  135 

of  air  in  greenhouses,  table,  99 

ol  air  leaving  coils  in  plenum  sys- 
tem, 143 

room  standard,  42 
Temp,  control  in  heating  sys.,  243 

Andrews  system,  244 

important  points  in,  247 

in  large  plants,  246 

Johnson  system,  248 

thermostat,  244 

National  system,  251 

Powers  system,  249 

principle  of  system,  243 

special  designs  of,  247,  252 

Sylphon  damper  control,  245 
Thermofiers,   Belvac,   175 
Thermostat,  244 

thermostatic  valve.  174 
Traps,  high  pressure  steam,  110 

low  pressure  steam,  110 

Under-  fed  furnaces.  62 

Use  of  hot  water  in  indirect  coils  146 


Vacuum  systems,  79,  169 
Values  of  V.  140 

of  'k,'  36,  141 

of  'n.'  41 

Of  't.'  42,  43 


INDEX 


Valves,  air.  91 

automatic  vacuum.  177 

modulation  valve.  175 

thennostatic,  174 

types  of,  192 

Velocity   of    air   by    application   of 
heat,  28 

of  air  escaping  to  atmosphere,  151 
Vent  registers  (net),  51 

stacks,  69 
Ventilation  heat  loss.  88 

air  required  per  person,  19 
Vento  coils,  values  of  'k'  for.  141 
Vertical  hot  air  flues,  table.  297 
Volume  and  wt.  of  dry  air,  table,  286 

Warm  air  fur.,  cap.  of,  table  296 
air  heating  cap.,  297 


Washing  and  humidifying  of  air,  131 
Water,  conversion  factors,  table.  285 

hammer,  110 

needed  per  hour  in  dist.  htg.,  201 

pressure  in  mains.  203 

pressure,  table  of.  205 

seal  motor,  Webster.  173 

weight  of  column  corresponding  to 
air  pressure  in  ozs..  298 

weight  of  pure,  table  of.  287 

weight  of  water  and  air.  table,  289 
Weight  of  pure  water,  287 

of  water  and  air.  table.  289 
Work  done  in  moving  air,  154 
Wrought  iron  and  steel  pipes,  table, 
299 

expansion  of.  table,  300 


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